Turn off LTO again for Official Win/Clang LLD builds

We're not working on this config at the moment, so having a red buildbot
testing it is just waste of cycles.

BUG=688123, 598772

Review-Url: https://codereview.chromium.org/2677593002
Cr-Commit-Position: refs/heads/master@{#447910}

build/config/compiler/BUILD.gn

@@ -1490,9 +1490,8 @@ config("optimize_max") {
             # incremental value of C4702 for PGO builds is likely very small.
             "/wd4702",
           ]
-        } else if (is_clang && use_lld) {
-          cflags += [ "-flto" ]  # Link-time optimization (whole program optimization).
         }
+        # TODO(crbug.com/598772): Enable -flto for Clang.
       }
     } else if (optimize_for_fuzzing) {
       cflags = [ "-O1" ] + common_optimize_on_cflags