[lld][WebAssembly] Improve -v/-V/--version flag compat (#113204)

Fixes: #112836

Author: sbc100

lld/test/wasm/version.test

@@ -0,0 +1,12 @@
+## Copied from lld/test/ELF/version.test
+
+## --version skips input file processing.
+# RUN: wasm-ld --version %t/not-exist 2>&1 | FileCheck %s
+
+## -v/-V don't skip processing if there is any input.
+# RUN: wasm-ld -v 2>&1 | FileCheck %s
+# RUN: not wasm-ld -v %t/not-exist 2>&1 | FileCheck %s
+# RUN: wasm-ld -V 2>&1 | FileCheck %s
+# RUN: not wasm-ld -V %t/not-exist 2>&1 | FileCheck %s
+
+# CHECK: LLD {{.+}}

lld/wasm/Driver.cpp

@@ -1218,11 +1218,9 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
     return;
   }
 
-  // Handle --version
-  if (args.hasArg(OPT_version) || args.hasArg(OPT_v)) {
+  // Handle -v or -version.
+  if (args.hasArg(OPT_v) || args.hasArg(OPT_version))
     lld::outs() << getLLDVersion() << "\n";
-    return;
-  }
 
   // Handle --reproduce
   if (const char *path = getReproduceOption(args)) {
@@ -1248,6 +1246,13 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
   readConfigs(args);
   setConfigs();
 
+  // The behavior of -v or --version is a bit strange, but this is
+  // needed for compatibility with GNU linkers.
+  if (args.hasArg(OPT_v) && !args.hasArg(OPT_INPUT))
+    return;
+  if (args.hasArg(OPT_version))
+    return;
+
   createFiles(args);
   if (errorCount())
     return;

lld/wasm/Options.td

@@ -288,6 +288,7 @@ def: Flag<["-"], "S">, Alias<strip_debug>, HelpText<"Alias for --strip-debug">;
 def: Flag<["-"], "t">, Alias<trace>, HelpText<"Alias for --trace">;
 def: JoinedOrSeparate<["-"], "y">, Alias<trace_symbol>, HelpText<"Alias for --trace-symbol">;
 def: JoinedOrSeparate<["-"], "u">, Alias<undefined>;
+def: Flag<["-"], "V">, Alias<v>, HelpText<"Alias for -v">;
 
 // LTO-related options.
 def lto_O: JJ<"lto-O">, MetaVarName<"<opt-level>">,