[Win32][ELF] Make CodeView a DebugInfoFormat only for COFF format (#8…

…7149)

We have many problems to use CodeView for a win32-elf target, e.g.,
#87140 and `error: .seh_* directives are not supported on this target`.

Fixes: #87140

clang/lib/Driver/ToolChains/MSVC.h

@@ -61,9 +61,8 @@ class LLVM_LIBRARY_VISIBILITY MSVCToolChain : public ToolChain {
   /// formats, and to DWARF otherwise. Users can use -gcodeview and -gdwarf to
   /// override the default.
   llvm::codegenoptions::DebugInfoFormat getDefaultDebugFormat() const override {
-    return getTriple().isOSBinFormatMachO()
-               ? llvm::codegenoptions::DIF_DWARF
-               : llvm::codegenoptions::DIF_CodeView;
+    return getTriple().isOSBinFormatCOFF() ? llvm::codegenoptions::DIF_CodeView
+                                           : llvm::codegenoptions::DIF_DWARF;
   }
 
   /// Set the debugger tuning to "default", since we're definitely not tuning

clang/test/Misc/win32-elf.c

@@ -0,0 +1,5 @@
+// Check that basic use of win32-elf targets works.
+// RUN: %clang -fsyntax-only -target x86_64-pc-win32-elf %s
+
+// RUN: %clang -fsyntax-only -target x86_64-pc-win32-elf -g %s -### 2>&1 | FileCheck %s -check-prefix=DEBUG-INFO
+// DEBUG-INFO: -dwarf-version={{.*}}