tools, ci: print info to use v symlink instead of v symlink -githubci (#21471)

.github/workflows/symlink_ci.yml

@@ -49,8 +49,9 @@ jobs:
           rm $(which v)
           v --version && exit 1 || exit 0
       - name: Symlink (-githubci)
+        run: ./v symlink -githubci
+      - name: Test after symlink with -githubci (in a separate script)
         run: |
-          ./v symlink --githubci
           cd /tmp/ && v version
           cd ~ && v version
           echo 'println(123)' > hi.v

cmd/tools/vsymlink/vsymlink.v

@@ -4,17 +4,20 @@ const vexe = os.real_path(os.getenv_opt('VEXE') or { @VEXE })
 
 fn main() {
 	at_exit(|| os.rmdir_all(os.vtmp_dir()) or {}) or {}
-
-	if os.args.len > 3 {
-		print('usage: v symlink [OPTIONS]')
+	if os.args.len > 2 {
+		if '-githubci' in os.args {
+			// TODO: [AFTER 2024-09-31] remove `-githubci` flag and function and only print usage and exit(1) .
+			if os.getenv('GITHUB_JOB') != '' {
+				println('::warning::Use `v symlink` instead of `v symlink -githubci`')
+			}
+			setup_symlink_github()
+			return
+		} else {
+			println('usage: v symlink')
 			exit(1)
 		}
-
-	if '-githubci' in os.args {
-		setup_symlink_github()
-	} else {
-		setup_symlink()
 	}
+	setup_symlink()
 }
 
 fn setup_symlink_github() {