Report warning when two .kt files get same paths in JS source map

compiler/testData/cli/js/sourceMapDuplicatePath/bar/lib.kt

@@ -0,0 +1 @@
+fun bar() = foo() + "bar"

compiler/testData/cli/js/sourceMapDuplicatePath/foo/lib.kt

@@ -0,0 +1 @@
+fun foo() = "foo"

compiler/testData/cli/js/sourceMapDuplicateRelativePaths.args

@@ -0,0 +1,7 @@
+$TESTDATA_DIR$/sourceMapDuplicatePath/
+-no-stdlib
+-source-map
+-source-map-source-roots
+$TESTDATA_DIR$/sourceMapDuplicatePath/foo:$TESTDATA_DIR$/sourceMapDuplicatePath/bar
+-output
+$TEMP_DIR$/out.js

compiler/testData/cli/js/sourceMapDuplicateRelativePaths.out

@@ -0,0 +1,2 @@
+warning: there are files with same path 'lib.kt', relative to source roots: '$TESTDATA_DIR$/sourceMapDuplicatePath/foo/lib.kt' and '$TESTDATA_DIR$/sourceMapDuplicatePath/bar/lib.kt'. This will likely cause problems with debugger
+OK

compiler/testData/cli/js/sourceMapDuplicateRelativePaths.test

@@ -0,0 +1,2 @@
+// EXISTS: out.js
+// EXISTS: out.js.map