[Build] Refine check for SWT native binary rebuild commit

Currently the build is aborted if the branch tip is at a commit, which
was committed with the email of the 'Eclipse Platform Bot'. This is done
to prevent rebuilds after a commit for a SWT native binary rebuild was
pushed by the bot. But because that bot is also used for other kind of
commits, this test leads to false positives.

This reworks the pipeline to check if the head commit has a
SWT-native-binary build tag attached, which is a more precise indicator.

This also fixes the check if a native rebuild is enforced, when testing
if the build can be skipped.

Author: HannesWell

Jenkinsfile

@@ -42,6 +42,7 @@ def runOnNativeBuildAgent(String platform, Closure body) {
 	}
 }
 
+
 /** 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)) {
@@ -70,8 +71,10 @@ def getNativeJdkUrl(String os, String arch) { // To update the used JDK version
 	return "https://download.eclipse.org/justj/jres/17/downloads/20230428_1804/org.eclipse.justj.openjdk.hotspot.jre.minimal.stripped-17.0.7-${os}-${arch}.tar.gz"
 }
 
+nativeBinariesTagPattern = 'v[0-9][0-9][0-9][0-9]r*'
+
 def getLatestGitTag() {
-	return sh(script: 'git describe --abbrev=0 --tags --match v[0-9][0-9][0-9][0-9]*', returnStdout: true).trim()
+	return sh(script: "git describe --abbrev=0 --tags --match ${nativeBinariesTagPattern}", returnStdout: true).trim()
 }
 
 def getSWTVersions() { // must be called from the repository root
@@ -114,26 +117,24 @@ pipeline {
 				dir('eclipse.platform.swt') {
 					checkout scm
 					script {
-						def authorMail = sh(script: 'git log -1 --pretty=format:"%ce" HEAD', returnStdout: true)
-						echo 'HEAD commit author: ' + authorMail
-						def buildBotMail = '[email protected]'
-						if (buildBotMail.equals(authorMail) && !params.forceNativeBuilds) {
-							// Prevent endless build-loops due to self triggering because of a previous automated build of natives and the associated updates.
-							currentBuild.result = 'ABORTED'
-							error('Abort build only triggered by automated SWT-natives update.')
-						}
-						sh """
+						sh '''
 						java -version
 						git version
 						git lfs version
-						git config --global user.email '${buildBotMail}'
+						git config --global user.email '[email protected]'
 						git config --global user.name 'Eclipse Platform Bot'
 						git config --unset core.hooksPath # Jenkins disables hooks by default as security feature, but we need the hooks for LFS
 						git lfs update # Install Git LFS hooks in repository, which has been skipped due to the initially nulled hookspath
 						git lfs pull
 						git fetch --all --tags --quiet
 						git remote set-url --push origin [email protected]:eclipse-platform/eclipse.platform.swt.git
-						"""
+						'''
+						def launcherTagsAtCommit = sh(script: "git tag --points-at HEAD --list '${nativeBinariesTagPattern}'", returnStdout: true).trim()
+						if (!launcherTagsAtCommit.isEmpty() && !params.any{ e -> e.key.startsWith('forceNativeBuilds-') && e.value }) {
+							// Prevent endless build-loops due to self triggering because of a previous automated build of natives and the associated updates.
+							currentBuild.result = 'ABORTED'
+							error('Abort build only triggered by automated SWT-natives update.')
+						}
 					}
 				}
 			}