[K/N][tests] Do not propagate user.dir property to compiler/cinterop

In a Gradle process, the user.dir property is set to the directory
where the build was started. By default, if we start a child process
via project.javaexec, Gradle sets its working directory to the
directory of the current project. But passing Gradle's value of user.dir
to that process overrides this setting.

This makes tools started in a such way sensitive to directory the build
is started from. Thus a test using relative paths may fail if it is
started from a wrong directory.

This patch fixes this issue for Kotlin/Native tests.

kotlin-native/backend.native/tests/interop/embedStaticLibraries/embedStaticLibraries.def

@@ -1,2 +1,2 @@
-libraryPaths = kotlin-native/backend.native/tests/build/embedStaticLibraries
+libraryPaths = build/embedStaticLibraries
 staticLibraries = 3.a 4.a

kotlin-native/backend.native/tests/interop/kt43502/kt43502.def

@@ -1,2 +1,2 @@
-libraryPaths = kotlin-native/backend.native/tests/build/kt43502
+libraryPaths = build/kt43502
 staticLibraries = kt43502.a

kotlin-native/tools/kotlin-native-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/konan/KonanToolRunner.kt

@@ -58,7 +58,10 @@ internal abstract class KonanCliRunner(
     }
 
     protected val blacklistProperties: Set<String> =
-        setOf("java.endorsed.dirs")
+        setOf(
+                "java.endorsed.dirs", // Fix for KT-25887
+                "user.dir"            // Don't propagate the working dir of the current Gradle process
+        )
 
     override val classpath: FileCollection =
             project.fileTree("$konanHome/konan/lib/")