[Build] Rename library files if native sources of platform are unchanged

Build only the SWT binaries whose native sources are really changed and
just rename the binaries for all other platforms that are not changed.

Avoiding a rebuild of effectively unchanged binaries has multiple
advantages, if only a sub-set of all supported platforms is build:
- reduced build times
- reduced occupation of precious native build-nodes in Jenkins
- increased stability of the build because if the native build-nodes
for the skipped platforms are unavailable the build isn't blocked
anymore.
- reduced future growth of the git large-file storage occupation as
renaming a binary file has basically zero-cost, while a modified binary
(even if just slightly) will add the entire file again.

Author: HannesWell

Jenkinsfile

@@ -42,8 +42,8 @@ def runOnNativeBuildAgent(String platform, Closure body) {
 	}
 }
 
-/** Returns the download URL of the JDK against whoose C headers (in the 'include/' folder) and native libraries the SWT natives are compiled.*/
-def getNativeJdkUrl(String os, String arch){ // To update the used JDK version update the URL template below
+/** Returns the download URL of the JDK against whose C headers (in the 'include/' folder) and native libraries the SWT natives are compiled.*/
+def getNativeJdkUrl(String os, String arch) { // To update the used JDK version update the URL template below
 	if('win32'.equals(os) && 'aarch64'.equals(arch)) {
 		// Temporary workaround until there are official Temurin GA releases for Windows on ARM that can be consumed through JustJ
 		dir("${WORKSPACE}/repackage-win32.aarch64-jdk") {
@@ -82,7 +82,7 @@ def getSWTVersions() { // must be called from the repository root
 	return props
 }
 
-boolean NATIVES_CHANGED = false
+Set NATIVES_CHANGED = []
 
 pipeline {
 	options {
@@ -103,7 +103,9 @@ pipeline {
 		PR_VALIDATION_BUILD = "true"
 	}
 	parameters {
-		booleanParam(name: 'forceNativeBuilds', defaultValue: false, description: 'Forces to run the native builds of swt\'s binaries. Will push the built binaries to the master branch, unless \'skipCommit\' is set. Useful in debugging.')
+		booleanParam(name: 'forceNativeBuilds-cocoa', defaultValue: false, description: 'Enforce a re-build of SWT\'s native binaries for Mac OS X. Will push the built binaries to the master branch, unless \'skipCommit\' is set.')
+		booleanParam(name: 'forceNativeBuilds-gtk', defaultValue: false, description: 'Enforce a re-build of SWT\'s native binaries for Linux. Will push the built binaries to the master branch, unless \'skipCommit\' is set.')
+		booleanParam(name: 'forceNativeBuilds-win32', defaultValue: false, description: 'Enforce a re-build of SWT\'s native binaries for Windows. Will push the built binaries to the master branch, unless \'skipCommit\' is set.')
 		booleanParam(name: 'skipCommit', defaultValue: false, description: 'Stops committing to swt and swt binaries repo at the end. Useful in debugging.')
 	}
 	stages {
@@ -141,9 +143,10 @@ pipeline {
 						git config --global user.name 'Eclipse Releng Bot'
 					'''
 					script {
+						def allWS = ['cocoa', 'gtk', 'win32']
+						def libraryFilePattern = [ 'cocoa' : 'libswt-*.jnilib', 'gtk' : 'libswt-*.so', 'win32' : 'swt-*.dll' ]
 						def swtTag = getLatestGitTag()
 						echo "Current tag=${swtTag}."
-						boolean nativesChanged = false
 						dir('bundles/org.eclipse.swt') {
 							// Verify preprocessing is completed
 							sh '''
@@ -154,34 +157,41 @@ pipeline {
 							'''
 							def sourceFoldersProps = readProperties(file: 'nativeSourceFolders.properties')
 							def sources = sourceFoldersProps.collectEntries{ k, src -> [ k, src.split(',').collect{ f -> '\'' + f + '\''}.join(' ') ] }
-							def diff = sh(script: "git diff HEAD ${swtTag} ${sources.values().join(' ')}", returnStdout: true)
-							nativesChanged = !diff.strip().isEmpty()
-							echo "Natives changed since ${swtTag}: ${nativesChanged}"
+							for(ws in allWS) {
+								def diff = sh(script: "git diff HEAD ${swtTag} ${sources.src_common} ${sources['src_' + ws]}", returnStdout: true)
+								if (!diff.strip().isEmpty()) {
+									NATIVES_CHANGED += ws
+								}
+							}
+							echo "Natives changed since ${swtTag}: ${NATIVES_CHANGED.isEmpty() ? 'None': NATIVES_CHANGED}"
 						}
-						if (nativesChanged || params.forceNativeBuilds) {
-							NATIVES_CHANGED = true
-							def swtVersions = getSWTVersions()
-							withEnv(['swt_version='+swtVersions['swt_version'], 'new_version='+swtVersions['new_version'], 'rev='+swtVersions['rev'], 'new_rev='+swtVersions['new_rev'],
-									'comma_ver='+swtVersions['comma_ver'], "new_comma_ver=${swtVersions['maj_ver']},${swtVersions['min_ver']},${swtVersions['new_rev']},0" ]) {
-								sh '''
+						NATIVES_CHANGED += allWS.findAll{ ws -> params[ 'forceNativeBuilds-' + ws] }
+						if (!NATIVES_CHANGED.isEmpty()) {
+							def versions = getSWTVersions()
+							for(ws in allWS) {
+								if (NATIVES_CHANGED.contains(ws)) {
+								sh """
 									# Delete native binaries to be replaced by subsequent binaries build
-									rm binaries/org.eclipse.swt.gtk.*/libswt-*.so
-									rm binaries/org.eclipse.swt.win32.*/swt-*.dll
-									rm binaries/org.eclipse.swt.cocoa.*/libswt-*.jnilib
-									
-									echo "Incrementing version from ${swt_version} to ${new_version}; new comma_ver=${new_comma_ver}"
+									rm binaries/org.eclipse.swt.${ws}.*/*swt-*.${libraryFilePattern[ws]}
 									
-									libraryFile='bundles/org.eclipse.swt/Eclipse SWT PI/common/org/eclipse/swt/internal/Library.java'
-									sed -i -e "s/REVISION = ${rev}/REVISION = ${new_rev}/g" "$libraryFile"
-									
-									commonMakeFile='bundles/org.eclipse.swt/Eclipse SWT/common/library/make_common.mak'
-									sed -i -e "s/rev=${rev}/rev=${new_rev}/g" "$commonMakeFile"
-									sed -i -e "s/comma_ver=${comma_ver}/comma_ver=${new_comma_ver}/g" "$commonMakeFile"
-								'''
+									echo "Incrementing version from ${versions.swt_version} to ${versions.new_version}"
+									sed -i -e "s/REVISION = ${versions.rev}/REVISION = ${versions.new_rev}/g" \
+										'bundles/org.eclipse.swt/Eclipse SWT PI/common/org/eclipse/swt/internal/Library.java'
+									sed -i -e "s/rev=${versions.rev}/rev=${versions.new_rev}/g" \
+										'bundles/org.eclipse.swt/Eclipse SWT/common/library/make_common.mak'
+								"""
+								} else {
+									// Just rename existing native library files to new revision instead of rebuilding them
+									sh """
+										for f in binaries/org.eclipse.swt.${ws}.*/*swt-*.${libraryFilePattern[ws]}; do
+											mv "\$f" "\$(echo \$f | sed 's/-${ws}-${versions.swt_version}/-${ws}-${versions.new_version}/g')"
+										done
+									"""
+								}
 							}
 							// Collect SWT-native's sources
 							dir('bundles/org.eclipse.swt') {
-								for (ws in ['cocoa', 'gtk', 'win32']) {
+								for (ws in NATIVES_CHANGED) {
 									sh "java -Dws=${ws} build-scripts/CollectSources.java -nativeSources 'target/natives-build-temp/${ws}'"
 									dir("target/natives-build-temp/${ws}") {
 										stash(name:"swt.binaries.sources.${ws}")
@@ -214,13 +224,17 @@ pipeline {
 					}
 				}
 				stages {
-					stage('Build SWT-natives') {
+					stage('Prepare and post-process native build') {
 						options {
 							timeout(time: 120, unit: 'MINUTES') // Some build agents are rare and it might take awhile until they are available.
 						}
 						steps {
 							script {
 								def (ws, os, arch) = env.PLATFORM.split('\\.')
+								if (!NATIVES_CHANGED.contains(ws)) {
+									echo "Skip native build for unchanged platform ${PLATFORM}"
+									return;
+								}
 								dir("jdk-download-${os}.${arch}") {
 									// Fetch the JDK, which provides the C header-files and shared native libraries, against which the natives are build.
 									sh "curl ${getNativeJdkUrl(os, arch)} | tar -xzf - include/ lib/"
@@ -235,7 +249,7 @@ pipeline {
 										unstash "jdk.resources.${os}.${arch}"
 									}
 									withEnv(['MODEL=' + arch, "OUTPUT_DIR=${WORKSPACE}/libs", "SWT_JAVA_HOME=${WORKSPACE}/jdk.resources"]) {
-										if (isUnix()){
+										if (isUnix()) {
 											sh '''#!/bin/bash -x
 												mkdir libs
 												if [[ ${PLATFORM} == gtk.linux.* ]]; then
@@ -269,10 +283,7 @@ pipeline {
 									cleanWs() // workspace not cleaned by default
 								}
 							}
-						}
-					}
-					stage('Collect and sign binaries') {
-						steps {
+							// Collect and sign binaries
 							dir("libs/${PLATFORM}") {
 								unstash "swt.binaries.${PLATFORM}"
 								sh '''#!/bin/bash -x