Compile common stdlib tests against common stdlib

Declare platform-specific test utilities as expect.

libraries/stdlib/common/build.gradle

@@ -4,7 +4,8 @@ apply plugin: 'kotlin-platform-common'
 
 configurePublishing(project)
 
-ext.commonSrcDir = "${buildDir}/common-sources"
+def commonSrcDir = "${buildDir}/common-sources"
+def commonTestSrcDir = "${buildDir}/common-test-sources"
 
 sourceSets {
     main {
@@ -13,9 +14,21 @@ sourceSets {
             srcDir commonSrcDir
         }
     }
+    test {
+        kotlin {
+            srcDir commonTestSrcDir
+            srcDir 'test'
+        }
+    }
+}
+
+dependencies {
+    testCompile project(":kotlin-test:kotlin-test-common")
+    testCompile project(":kotlin-test:kotlin-test-annotations-common")
 }
 
 createPreprocessorTask(project, "Main", "${projectDir}/../src/kotlin", commonSrcDir)
+createPreprocessorTask(project, "Test", "${projectDir}/../test", commonTestSrcDir)
 
 compileKotlinCommon {
     dependsOn preprocessSourcesMain
@@ -34,6 +47,10 @@ compileKotlinCommon {
 }
 */
 
+compileTestKotlinCommon {
+    dependsOn preprocessSourcesTest
+}
+
 kotlin.experimental.coroutines 'enable'
 
 jar {