[clang] [MinGW] Let the last of -mconsole/-mwindows have effect

[mstorsjo]

Summary

Don't just check for the existence of one, but check which one was
specified last, if any.

This fixes https://llvm.org/PR51296.

[mati865]

LGTM

clang/lib/Driver/ToolChains/MinGW.cpp

case llvm::Triple::thumb:
     break;
   case llvm::Triple::aarch64:
     CmdArgs.push_back("arm64pe");
     break;
   default:
     llvm_unreachable("Unsupported target architecture.");
   }
 
-  if (Args.hasArg(options::OPT_mwindows)) {
+  Arg *SubsysArg =
+      Args.getLastArg(options::OPT_mwindows, options::OPT_mconsole);
+  if (SubsysArg && SubsysArg->getOption().matches(options::OPT_mwindows)) {
     CmdArgs.push_back("--subsystem");
     CmdArgs.push_back("windows");
-  } else if (Args.hasArg(options::OPT_mconsole)) {
+  } else if (SubsysArg &&
+             SubsysArg->getOption().matches(options::OPT_mconsole)) {
     CmdArgs.push_back("--subsystem");
     CmdArgs.push_back("console");
   }
 
   if (Args.hasArg(options::OPT_mdll))
     CmdArgs.push_back("--dll");
   else if (Args.hasArg(options::OPT_shared))
     CmdArgs.push_back("--shared");

clang/test/Driver/mingw.cpp

 // CHECK_MINGW_UBUNTU_POSIX_TREE: "[[BASE]]/Inputs/mingw_ubuntu_posix_tree/usr{{/|\\\\}}lib{{/|\\\\}}gcc{{/|\\\\}}x86_64-w64-mingw32{{/|\\\\}}10.2-posix{{/|\\\\}}include{{/|\\\\}}c++{{/|\\\\}}x86_64-w64-mingw32"
 // CHECK_MINGW_UBUNTU_POSIX_TREE: "[[BASE]]/Inputs/mingw_ubuntu_posix_tree/usr{{/|\\\\}}lib{{/|\\\\}}gcc{{/|\\\\}}x86_64-w64-mingw32{{/|\\\\}}10.2-posix{{/|\\\\}}include{{/|\\\\}}c++{{/|\\\\}}backward"
 // CHECK_MINGW_UBUNTU_POSIX_TREE: "[[BASE]]/Inputs/mingw_ubuntu_posix_tree/usr{{/|\\\\}}x86_64-w64-mingw32{{/|\\\\}}include"
 
 // RUN: %clang -target i686-windows-gnu -E -### %s 2>&1 | FileCheck -check-prefix=CHECK_MINGW_NO_UNICODE %s
 // RUN: %clang -target i686-windows-gnu -E -### %s -municode 2>&1 | FileCheck -check-prefix=CHECK_MINGW_UNICODE %s
 // CHECK_MINGW_NO_UNICODE-NOT: "-DUNICODE"
 // CHECK_MINGW_UNICODE: "-DUNICODE"
+
+// RUN: %clang -target i686-windows-gnu -### %s 2>&1 | FileCheck -check-prefix=CHECK_NO_SUBSYS %s
+// RUN: %clang -target i686-windows-gnu -### %s -mwindows -mconsole 2>&1 | FileCheck -check-prefix=CHECK_SUBSYS_CONSOLE %s
+// RUN: %clang -target i686-windows-gnu -### %s -mconsole -mwindows 2>&1 | FileCheck -check-prefix=CHECK_SUBSYS_WINDOWS %s
+// CHECK_NO_SUBSYS-NOT: "--subsystem"
+// CHECK_SUBSYS_CONSOLE: "--subsystem" "console"
+// CHECK_SUBSYS_WINDOWS: "--subsystem" "windows"