[clang][Driver] Pick the last --driver-mode in case of multiple ones

This was an accidental behaviour change in D106789 and this patch
restores it back to original state.

Differential Revision: https://reviews.llvm.org/D109361

clang/lib/Driver/Driver.cpp

@@ -5569,7 +5569,6 @@ llvm::StringRef clang::driver::getDriverMode(StringRef ProgName,
     if (!Arg.startswith(OptName))
       continue;
     Opt = Arg;
-    break;
   }
   if (Opt.empty())
     Opt = ToolChain::getTargetAndModeFromProgramName(ProgName).DriverMode;

clang/unittests/Driver/ToolChainTest.cpp

@@ -16,6 +16,7 @@
 #include "clang/Basic/LLVM.h"
 #include "clang/Driver/Compilation.h"
 #include "clang/Driver/Driver.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/VirtualFileSystem.h"
@@ -357,4 +358,10 @@ TEST(ToolChainTest, PostCallback) {
   EXPECT_TRUE(CallbackHasCalled);
 }
 
+TEST(GetDriverMode, PrefersLastDriverMode) {
+  static constexpr const char *Args[] = {"clang-cl", "--driver-mode=foo",
+                                         "--driver-mode=bar", "foo.cpp"};
+  EXPECT_EQ(getDriverMode(Args[0], llvm::makeArrayRef(Args).slice(1)), "bar");
+}
+
 } // end anonymous namespace.