Specify common sources for stdlib test compilation tasks

Some multiplatform tests are compiled in single-platform projects:
- in kotlin-stdlib-jdk7
- in kotlin-stdlib-jdk8
- in kotlin-stdlib-js-ir. The latter is technically MPP but with a
single platform, so its common sources are not considered as common.

Pass information about common sources to test compilation tasks in order
to use OptionalExpectation annotations there.

libraries/stdlib/jdk7/build.gradle

diff --git a/libraries/stdlib/jdk7/build.gradle b/libraries/stdlib/jdk7/build.gradle
index 1e56622..361e0fd 100644
--- a/libraries/stdlib/jdk7/build.gradle
+++ b/libraries/stdlib/jdk7/build.gradle
@@ -90,6 +90,7 @@
             "-Xopt-in=kotlin.ExperimentalUnsignedTypes",
             "-Xopt-in=kotlin.ExperimentalStdlibApi",
             "-Xopt-in=kotlin.io.path.ExperimentalPathApi",
+            "-Xcommon-sources=${fileTree('../test').join(',')}",
     ]
 }
 

libraries/stdlib/jdk8/build.gradle

diff --git a/libraries/stdlib/jdk8/build.gradle b/libraries/stdlib/jdk8/build.gradle
index e59fbc3..a5e4526 100644
--- a/libraries/stdlib/jdk8/build.gradle
+++ b/libraries/stdlib/jdk8/build.gradle
@@ -82,6 +82,7 @@
             "-Xopt-in=kotlin.ExperimentalUnsignedTypes",
             "-Xopt-in=kotlin.ExperimentalStdlibApi",
             "-Xopt-in=kotlin.io.path.ExperimentalPathApi",
+            "-Xcommon-sources=${fileTree('../test').join(',')}",
     ]
 }
 

libraries/stdlib/js-ir/build.gradle.kts

diff --git a/libraries/stdlib/js-ir/build.gradle.kts b/libraries/stdlib/js-ir/build.gradle.kts
index 47ee64c..b43b8cc 100644
--- a/libraries/stdlib/js-ir/build.gradle.kts
+++ b/libraries/stdlib/js-ir/build.gradle.kts
@@ -149,6 +149,11 @@
     kotlinOptions.freeCompilerArgs += "-Xir-module-name=kotlin"
 }
 
+
+val compileTestKotlinJs by tasks.existing(KotlinCompile::class) {
+    kotlinOptions.freeCompilerArgs += "-Xcommon-sources=${kotlin.sourceSets["commonTest"].kotlin.joinToString(",")}"
+}
+
 val packFullRuntimeKLib by tasks.registering(Jar::class) {
     dependsOn(compileKotlinJs)
     from(buildDir.resolve("classes/kotlin/js/main"))