builder: bring back cross compilation for windows

vlib/v/builder/cc.v

@@ -490,8 +490,6 @@ If you're confident that all of the above is true, please try running V with the
 }
 
 fn (mut c Builder) cc_windows_cross() {
-	/*
-	QTODO
 	println('Cross compiling for Windows...')
 	if !c.pref.out_name.ends_with('.exe') {
 		c.pref.out_name += '.exe'
@@ -530,22 +528,24 @@ fn (mut c Builder) cc_windows_cross() {
 	obj_name = obj_name.replace('.o.o', '.o')
 	include := '-I $winroot/include '
 	*/
-	mut cmd := ''
-	cmd = ''
-	$if macos {
-		cmd = 'x86_64-w64-mingw32-gcc -std=gnu11 $args -municode'
-	}
-	$else {
+	if os.user_os() !in ['mac', 'darwin','linux'] {
+		println(os.user_os())
 		panic('your platform is not supported yet')
 	}
-
-	println(cmd)
+	mut cmd := 'x86_64-w64-mingw32-gcc'
+	cmd += ' -std=gnu11 $args -municode'
 	//cmd := 'clang -o $obj_name -w $include -m32 -c -target x86_64-win32 ${pref.default_module_path}/$c.out_name_c'
-	if c.pref.verbosity.is_higher_or_equal(.level_one) {
+	if c.pref.is_verbose {
 		println(cmd)
 	}
 	if os.system(cmd) != 0 {
-		println('Cross compilation for Windows failed. Make sure you have clang installed.')
+		println('Cross compilation for Windows failed. Make sure you have mingw-w64 installed.')
+		$if macos {
+			println('brew install mingw-w64')
+		}
+		$if linux {
+			println('sudo apt install -y mingw-w64')
+		}
 		exit(1)
 	}
 	/*
@@ -561,8 +561,7 @@ fn (mut c Builder) cc_windows_cross() {
 		// os.rm(obj_name)
 	}
 	*/
-	println('Done!')
-	*/
+	println(c.pref.out_name + ' has been successfully compiled')
 }
 
 fn (c &Builder) build_thirdparty_obj_files() {