win: Clean up coverage linker flags after clang r360674.

After clang r360674, each .obj file embeds the path to the profile library
as a dependent lib. No intended behavior change.

Change-Id: Ie892fccdb8aaefc2545db56fb3274dc6f0992a96
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1630986Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663751}

build/config/compiler/pgo/BUILD.gn

@@ -17,22 +17,10 @@ config("pgo_instrumentation_flags") {
   if (chrome_pgo_phase == 1) {
     if (is_clang) {
       cflags = [ "-fprofile-instr-generate" ]
-      if (is_win) {
-        # Normally, we pass -fprofile-instr-generate to the compiler and it
-        # automatically passes the right flags to the linker.
-        # However, on Windows, we call the linker directly, without going
-        # through the compiler driver. This means we need to pass the right
-        # flags ourselves.
-        _clang_rt_base_path =
-            "$clang_base_path/lib/clang/$clang_version/lib/windows"
-        if (target_cpu == "x86") {
-          _clang_rt_suffix = "-i386.lib"
-        } else if (target_cpu == "x64") {
-          _clang_rt_suffix = "-x86_64.lib"
-        }
-        assert(_clang_rt_suffix != "", "target CPU $target_cpu not supported")
-        ldflags += [ "$_clang_rt_base_path/clang_rt.profile$_clang_rt_suffix" ]
-      } else {
+      if (!is_win) {
+        # Windows directly calls link.exe instead of the compiler driver when
+        # linking, and embeds the path to the profile runtime library as
+        # dependent library into each object file.
         ldflags += [ "-fprofile-instr-generate" ]
       }
     } else if (is_win) {

build/config/coverage/BUILD.gn

@@ -8,21 +8,10 @@ config("default_coverage") {
   if (use_clang_coverage) {
     ldflags = []
     if (!is_win) {
-      ldflags += [ "-fprofile-instr-generate" ]
-    } else {
       # Windows directly calls link.exe instead of the compiler driver when
-      # linking.  Hence, pass the runtime libraries instead of
-      # -fsanitize=address.
-      # TODO(rnk): Come up with a more uniform approach for linking against
-      # compiler-rt for sanitizers and coverage.
-      if (target_cpu == "x64") {
-        ldflags += [ "clang_rt.profile-x86_64.lib" ]
-      } else if (target_cpu == "x86") {
-        ldflags += [ "clang_rt.profile-i386.lib" ]
-      } else {
-        assert(false &&
-               "use_clang_coverage=true not supported yet for this target_cpu")
-      }
+      # linking, and embeds the path to the profile runtime library as
+      # dependent library into each object file.
+      ldflags += [ "-fprofile-instr-generate" ]
     }
 
     cflags = [