discover mingw paths automatically

Author: ianbotsf

runtime/runtime-core/build.gradle.kts

@@ -1,3 +1,8 @@
+import aws.sdk.kotlin.gradle.util.prop
+import aws.sdk.kotlin.gradle.util.typedProp
+import java.nio.file.Files
+import java.nio.file.Paths
+
 /*
  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
  * SPDX-License-Identifier: Apache-2.0
@@ -57,19 +62,59 @@ kotlin {
 
 
     mingwX64 {
+        val mingwHome = findMingwHome()
+        val defPath = layout.buildDirectory.file("cinterop/winver.def")
+
+        // Dynamically construct def file because of dynamic mingw paths
+        val defFileTask by tasks.registering {
+            outputs.file(defPath)
+
+            val mingwLibs = Paths.get(mingwHome, "lib").toString().replace("\\", "\\\\") // Windows path shenanigans
+
+            doLast {
+                Files.writeString(
+                    defPath.get().asFile.toPath(),
+                    """
+                        package = aws.smithy.kotlin.native.winver
+                        headers = windows.h
+                        compilerOpts = \
+                            -DUNICODE \
+                            -DWINVER=0x0601 \
+                            -D_WIN32_WINNT=0x0601 \
+                            -DWINAPI_FAMILY=3 \
+                            -DOEMRESOURCE \
+                            -Wno-incompatible-pointer-types \
+                            -Wno-deprecated-declarations
+                        libraryPaths = $mingwLibs
+                        staticLibraries = libversion.a
+                    """.trimIndent(),
+                )
+            }
+        }
+
         compilations["main"].cinterops {
             create("winver") {
-                definitionFile.set(file("native/interop/winver.def"))
-                includeDirs("C:\\msys64\\mingw64\\include")
+                val mingwIncludes = Paths.get(mingwHome, "include").toString()
+                includeDirs(mingwIncludes)
+                definitionFile.set(defPath)
+
+                // Ensure that the def file is written first
+                tasks[interopProcessingTaskName].dependsOn(defFileTask)
             }
         }
 
         // TODO clean up
         val compilerArgs = listOf(
-            "-Xverbose-phases=Linker", // Enable verbose linking phase from the compiler
+            "-Xverbose-phases=linker", // Enable verbose linking phase from the compiler
             "-linker-option",
             "-v",
         )
         compilerOptions.freeCompilerArgs.addAll(compilerArgs)
     }
 }
+
+private fun findMingwHome(): String =
+    System.getenv("MINGW_PREFIX")?.takeUnless { it.isBlank() } ?:
+    typedProp("mingw.prefix") ?:
+    throw IllegalStateException("Cannot determine MinGW prefix location. Please verify MinGW is installed correctly " +
+            "and that either the `MINGW_PREFIX` environment variable or the `mingw.prefix` Gradle property is set.")