download vlib if it is missing

compiler/main.v

@@ -883,9 +883,17 @@ fn new_v(args[]string) &V {
 	//println('VROOT=$vroot')
 	// v.exe's parent directory should contain vlib
 	if !os.dir_exists(vroot) || !os.dir_exists(vroot + '/vlib/builtin') {
-		println('vlib not found. It should be next to the V executable. ')
-		println('Go to https://vlang.io to install V.')
-		exit(1)
+		println('vlib not found, downloading it...')
+		ret := os.system('git clone --depth=1 https://github.com/vlang/v .')
+		if ret != 0 {
+			println('failed to `git clone` vlib')
+			println('make sure you are online and have git installed')
+			exit(1)
+		}
+
+		//println('vlib not found. It should be next to the V executable. ')
+		//println('Go to https://vlang.io to install V.')
+		//exit(1)
 	}
 	//println('out_name:$out_name')
 	mut out_name_c := os.realpath( out_name ) + '.tmp.c'