Change format of -X arguments to require value after '='

Report a warning when an argument is passed in the old form (with the
whitespace)

 #KT-17264 Fixed

libraries/tools/runtime/build.gradle

@@ -43,7 +43,7 @@ compileKotlin {
     kotlinOptions {
         freeCompilerArgs = [
                 "-Xallow-kotlin-package",
-                "-Xdump-declarations-to", "${buildDir}/runtime-declarations.json",
+                "-Xdump-declarations-to=${buildDir}/runtime-declarations.json",
                 "-cp", "${rootDir}/../dist/builtins",
                 "-module-name", project.name
         ]