compiler: move v up implementation to tools/vup.v

tools/vup.v

@@ -0,0 +1,21 @@
+import os
+
+fn main() {
+	println('Updating V...')
+	vroot := os.dir(os.args[1])
+	os.chdir(vroot)
+	s := os.exec('git -C "$vroot" pull --rebase origin master') or { panic(err) }
+	println(s.output)
+	$if windows {
+		v_backup_file := '$vroot/v_old.exe'
+		if os.file_exists( v_backup_file ) {
+			os.rm( v_backup_file )
+		}
+		os.mv('$vroot/v.exe', v_backup_file)
+		s2 := os.exec('"$vroot/make.bat"') or { panic(err) }
+		println(s2.output)
+	} $else {
+		s2 := os.exec('make -C "$vroot"') or { panic(err) }
+		println(s2.output)
+	}
+}