[Driver] MinGW: Remove custom linker detection

This is a re-apply of rL313082 which was reverted in rL313088

In rL289668 the ability to specify the default linker at compile time
was added but because the MinGW driver used custom detection we could
not take advantage of this new CMAKE flag CLANG_DEFAULT_LINKER.

rL289668 added no test cases and the mingw driver was either overlooked
or purposefully skipped because it has some custom linker tests
Removing them here because they are covered by the generic case.

Reviewers: rnk

Differntial Revision: https://reviews.llvm.org/D37727

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@317397 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Driver/ToolChains/MinGW.cpp

@@ -107,14 +107,6 @@ void tools::MinGW::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   // handled somewhere else.
   Args.ClaimAllArgs(options::OPT_w);
 
-  StringRef LinkerName = Args.getLastArgValue(options::OPT_fuse_ld_EQ, "ld");
-  if (LinkerName.equals_lower("lld")) {
-    CmdArgs.push_back("-flavor");
-    CmdArgs.push_back("gnu");
-  } else if (!LinkerName.equals_lower("ld")) {
-    D.Diag(diag::err_drv_unsupported_linker) << LinkerName;
-  }
-
   if (!D.SysRoot.empty())
     CmdArgs.push_back(Args.MakeArgString("--sysroot=" + D.SysRoot));
 
@@ -244,7 +236,7 @@ void tools::MinGW::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
       if (Args.hasArg(options::OPT_static))
         CmdArgs.push_back("--end-group");
-      else if (!LinkerName.equals_lower("lld"))
+      else
         AddLibGCC(Args, CmdArgs);
     }
 
@@ -255,7 +247,7 @@ void tools::MinGW::Linker::ConstructJob(Compilation &C, const JobAction &JA,
       CmdArgs.push_back(Args.MakeArgString(TC.GetFilePath("crtend.o")));
     }
   }
-  const char *Exec = Args.MakeArgString(TC.GetProgramPath(LinkerName.data()));
+  const char *Exec = Args.MakeArgString(TC.GetLinkerPath());
   C.addCommand(llvm::make_unique<Command>(JA, *this, Exec, CmdArgs, Inputs));
 }
 

test/Driver/mingw-useld.c

-// RUN: %clang -### -target i686-pc-windows-gnu --sysroot=%S/Inputs/mingw_clang_tree/mingw32 %s 2>&1 | FileCheck -check-prefix=CHECK_LD_32 %s
-// CHECK_LD_32: ld{{(.exe)?}}"
-// CHECK_LD_32: "i386pe"
-// CHECK_LD_32-NOT: "-flavor" "gnu"
-
-// RUN: %clang -### -target i686-pc-windows-gnu --sysroot=%S/Inputs/mingw_clang_tree/mingw32 %s -fuse-ld=lld 2>&1 | FileCheck -check-prefix=CHECK_LLD_32 %s
-// CHECK_LLD_32-NOT: invalid linker name in argument
-// CHECK_LLD_32: lld{{(.exe)?}}" "-flavor" "gnu"
-// CHECK_LLD_32: "i386pe"
-
-// RUN: %clang -### -target x86_64-pc-windows-gnu --sysroot=%S/Inputs/mingw_clang_tree/mingw32 %s -fuse-ld=lld 2>&1 | FileCheck -check-prefix=CHECK_LLD_64 %s
-// CHECK_LLD_64-NOT: invalid linker name in argument
-// CHECK_LLD_64: lld{{(.exe)?}}" "-flavor" "gnu"
-// CHECK_LLD_64: "i386pep"
-
-// RUN: %clang -### -target arm-pc-windows-gnu --sysroot=%S/Inputs/mingw_clang_tree/mingw32 %s -fuse-ld=lld 2>&1 | FileCheck -check-prefix=CHECK_LLD_ARM %s
-// CHECK_LLD_ARM-NOT: invalid linker name in argument
-// CHECK_LLD_ARM: lld{{(.exe)?}}" "-flavor" "gnu"
-// CHECK_LLD_ARM: "thumb2pe"