Revert "Let lld emit colored diagnostics when invoked from ninja."

This reverts commit 00db3ddc.

Reason for revert: Breaks Linux CFI build here: https://ci.chromium.org/buildbot/chromium.memory/Linux%20CFI/8024

Original change's description:
> Let lld emit colored diagnostics when invoked from ninja.
> 
> Bug: 841221
> Change-Id: I72d13c78a2c623865a4f29542d25f6b3488b350b
> Reviewed-on: https://chromium-review.googlesource.com/1067460
> Reviewed-by: Reid Kleckner <rnk@chromium.org>
> Commit-Queue: Nico Weber <thakis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#560343}

TBR=thakis@chromium.org,rnk@chromium.org

Change-Id: I3811083daa622dca605ca32be5cc4c7098b60b4a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 841221
Reviewed-on: https://chromium-review.googlesource.com/1067949Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#560345}

build/config/compiler/BUILD.gn

@@ -485,19 +485,6 @@ config("compiler") {
     cflags += [ "-fmerge-all-constants" ]
   }
 
-  if (use_lld) {
-    # TODO(thakis): Make the driver pass --color-diagnostics to the linker
-    # if -fcolor-diagnostics is passed to it, and pass -fcolor-diagnostics
-    # in ldflags instead.
-    if (is_win) {
-      # On Windows, we call the linker directly, instead of calling it through
-      # the driver.
-      ldflags += [ "--color-diagnostics" ]
-    } else {
-      ldflags += [ "-Wl,--color-diagnostics" ]
-    }
-  }
-
   if (is_clang && !is_nacl && current_toolchain == host_toolchain &&
       target_os != "chromeos") {
     cflags += [