Run tests in kotlin-gradle-plugin in repository working dir

Unify with other modules and make GradleNodeModuleBuilderTest work under
JPS.

libraries/tools/kotlin-gradle-plugin/build.gradle.kts

@@ -144,6 +144,8 @@ tasks {
 projectTest {
     executable = "${rootProject.extra["JDK_18"]!!}/bin/java"
     dependsOn(tasks.named("validateTaskProperties"))
+
+    workingDir = rootDir
 }
 
 pluginBundle {

libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/targets/js/npm/GradleNodeModuleBuilderTest.kt

@@ -16,7 +16,7 @@ class GradleNodeModuleBuilderTest {
     @Test
     fun validPackageJsonWithoutDependencies() {
         val packageJson = fromSrcPackageJson(
-            File("src/test/resources/org/jetbrains/kotlin/gradle/targets/js/npm/GradleNodeModuleBuilderTest/package.json")
+            File("libraries/tools/kotlin-gradle-plugin/src/test/resources/org/jetbrains/kotlin/gradle/targets/js/npm/GradleNodeModuleBuilderTest/package.json")
         )
         assertNotNull(packageJson, "package.json should be deserialized")