[JPS] Fix KotlinJvmModuleBuildTarget.findJavaSourceRoots to only return Java source roots

This change is needed because otherwise, source files that are not Java will be added as `JavaSourceRoot`, this is incorrect and causes assertion error in `com.intellij.core.JavaCoreProjectEnvironment.addSourcesToClasspath`. Refer to KT-65325 for more context.


Merge-request: KT-MR-14088
Merged-by: Xuan Son Trinh <xuanson.trinh@jetbrains.com>

jps/jps-plugin/jps-tests/test/org/jetbrains/kotlin/jps/build/KotlinJpsBuildTest.kt

@@ -946,6 +946,12 @@ open class KotlinJpsBuildTest : KotlinJpsBuildTestBase() {
         checkWhen(emptyArray(), null, packageClasses("kotlinProject", "src/test1.kt", "Test1Kt"))
     }
 
+    @WorkingDir("KotlinProjectWithSingleKotlinFileAsSourceRoot")
+    fun testBuildProjectWithSingleKotlinFileAsSource() {
+        initProject(JVM_MOCK_RUNTIME)
+        buildAllModules().assertSuccessful()
+    }
+
     fun testBuildAfterGdwBuild() {
         initProject(JVM_FULL_RUNTIME)
         findModule("module2").let {