Allow specifying arbitrary additional compiler flags

Author: dkhalanskyjb

buildSrc/src/main/kotlin/CommunityProjectsBuild.kt

@@ -181,3 +181,13 @@ fun KotlinCommonCompilerOptions.configureKotlinUserProject() {
         "-Xrender-internal-diagnostic-names", // render the diagnostic names in CLI
     )
 }
+
+/**
+ * Additional compiler flags passed on a case-by-case basis. Should be applied after the other flags.
+ * See <https://github.com/Kotlin/kotlinx.coroutines/pull/4392#issuecomment-2775630200>
+ */
+fun KotlinCommonCompilerOptions.addExtraCompilerFlags(project: Project) {
+    (project.rootProject.properties["kotlin_additional_cli_options"] as? String)?.split(" ")?.forEach {
+        if (it.isNotEmpty()) freeCompilerArgs.add(it)
+    }
+}

buildSrc/src/main/kotlin/configure-compilation-conventions.gradle.kts

@@ -27,7 +27,8 @@ configure(subprojects) {
                 freeCompilerArgs.addAll(
                     "-Xno-param-assertions",
                     "-Xno-call-assertions",
-                    "-Xno-receiver-assertions"
+                    "-Xno-receiver-assertions",
+                    "-Xjvm-default=disable",
                 )
             }
             if (this@configureEach is KotlinNativeCompile) {
@@ -37,6 +38,7 @@ configure(subprojects) {
                     "kotlin.experimental.ExperimentalNativeApi",
                 )
             }
+            addExtraCompilerFlags(project)
         }
 
     }

buildSrc/src/main/kotlin/kotlin-multiplatform-conventions.gradle.kts

@@ -15,10 +15,7 @@ kotlin {
     jvm {
         compilations.all {
             compileTaskProvider.configure {
-                compilerOptions {
-                    jvmTarget = JvmTarget.JVM_1_8
-                    freeCompilerArgs.addAll("-Xjvm-default=disable")
-                }
+                compilerOptions.jvmTarget = JvmTarget.JVM_1_8
             }
         }
     }