cmd/link: support .def file with MSVC clang toolchain

lld-link supports .def file, but requires a "-def:" (or "/def:")
flag. (MinGW linker, on the other hand, requires no flag.) Pass
the flag when using MSVC-based toolchain.

CL originally authored by Chressie Himpel.

Change-Id: I8c327ab48d36b0bcbb1d127cff544ffdb06be38e
Reviewed-on: https://go-review.googlesource.com/c/go/+/708716
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Chressie Himpel <[email protected]>

Author: cherrymui

src/cmd/link/internal/ld/lib.go

@@ -1787,9 +1787,13 @@ func (ctxt *Link) hostlink() {
 	case ctxt.IsAIX():
 		fileName := xcoffCreateExportFile(ctxt)
 		argv = append(argv, "-Wl,-bE:"+fileName)
-	case ctxt.IsWindows() && !slices.Contains(flagExtldflags, "-Wl,--export-all-symbols"):
+	case ctxt.IsWindows() && !slices.Contains(flagExtldflags, wlPrefix+"export-all-symbols"):
 		fileName := peCreateExportFile(ctxt, filepath.Base(outopt))
-		argv = append(argv, fileName)
+		prefix := ""
+		if isMSVC {
+			prefix = "-Wl,-def:"
+		}
+		argv = append(argv, prefix+fileName)
 	}
 
 	const unusedArguments = "-Qunused-arguments"