Drop "-sourceFiles" in kotlinc-js

Use free arguments instead, as is done in kotlinc-jvm and all sensible
compilers everywhere

Also fix some cases of AntTaskTest to be able to run them locally

compiler/testData/cli/js/outputPostfixFileNotFound.args

@@ -1,6 +1,5 @@
--sourceFiles
 $TESTDATA_DIR$/simple2js.kt
 -output
 $TEMP_DIR$/out.js
 -outputPostfix
-not/existing/path
+not/existing/path