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/stdlib/jre7/build.gradle

@@ -48,7 +48,7 @@ compileKotlin {
     kotlinOptions.freeCompilerArgs = [
             "-Xallow-kotlin-package",
             "-Xmultifile-parts-inherit",
-            "-Xdump-declarations-to", "${buildDir}/stdlib-jre7-declarations.json",
+            "-Xdump-declarations-to=${buildDir}/stdlib-jre7-declarations.json",
             "-module-name", project.name
     ]
 }