Minor, expand TESTDATA_DIR with absolute path in CLI tests

To be able to use it correctly inside an xml build file where, if the
path is not absolute, it's treated as relative to the build file path
(which is TMP_DIR in several tests of the subsequent commit)

compiler/testData/cli/jvm/duplicateSources.out

@@ -1,2 +1,2 @@
-warning: duplicate source root: compiler/testData/cli/jvm/simple.kt
+warning: duplicate source root: $TESTDATA_DIR$/simple.kt
 OK

compiler/testData/cli/jvm/jdkPathDoesNotExist.out

@@ -1,2 +1,2 @@
-error: JDK home directory does not exist: compiler/testData/cli/jvm/abacaba
+error: JDK home directory does not exist: $TESTDATA_DIR$/abacaba
 COMPILATION_ERROR

compiler/testData/cli/jvm/wrongJdkPath.out

@@ -1,2 +1,2 @@
-error: no class roots are found in the JDK path: compiler/testData/cli/jvm
+error: no class roots are found in the JDK path: $TESTDATA_DIR$
 COMPILATION_ERROR