Revert of Enable LLD for POSIX LTO builds on Linux. (patchset #1 id:1 of...

Revert of Enable LLD for POSIX LTO builds on Linux. (patchset #1 id:1 of https://codereview.chromium.org/2877913003/ )

Reason for revert:
Breaks crash reporting.

BUG=716484

Original issue's description:
> Enable LLD for POSIX LTO builds on Linux.
>
> This is a stripped down version of (reverted)
> change: https://codereview.chromium.org/2831213006/
>
> That change was reverted because ThinLTO regresses the binary
> size too much. LLD was a harmless part of the change,
> so it's worth enabling it.
>
> Based on https://codereview.chromium.org/2844883002/ by
> krasin@chromium.org, who is no longer with Google.
>
> BUG=607968
> R=dpranke@chromium.org,thakis@chromium.org
>
> Review-Url: https://codereview.chromium.org/2877913003
> Cr-Commit-Position: refs/heads/master@{#471532}
> Committed: https://chromium.googlesource.com/chromium/src/+/e6a66337552cfd9a9af9471775ad5b67ee588b88

TBR=dpranke@chromium.org,thakis@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=607968

Review-Url: https://codereview.chromium.org/2900883002
Cr-Commit-Position: refs/heads/master@{#473733}

build/toolchain/toolchain.gni

@@ -17,6 +17,12 @@ declare_args() {
       is_clang && target_os == "linux" && !is_chromeos && target_cpu == "x64" &&
       is_official_build
 
+  # Set to true to use lld, the LLVM linker. This flag may be used on Windows
+  # with the shipped LLVM toolchain, or on Linux with a self-built top-of-tree
+  # LLVM toolchain (see llvm_force_head_revision in
+  # build/config/compiler/BUILD.gn).
+  use_lld = is_win && host_os != "win"
+
   # If used with allow_posix_link_time_opt, it enables the experimental support
   # of ThinLTO that links 3x-10x faster but (as of now) does not have all the
   # important optimizations such us devirtualization implemented. See also
@@ -60,12 +66,6 @@ declare_args() {
     # Clang compiler version. Clang files are placed at version-dependent paths.
     clang_version = "5.0.0"
   }
-
-  # Set to true to use lld, the LLVM linker. This flag may be used on Windows
-  # or Linux.
-  use_lld = (is_win && host_os != "win") ||
-            (allow_posix_link_time_opt && target_os == "linux" &&
-             !is_chromeos && target_cpu == "x64")
 }
 
 # Check target_os here instead of is_ios as this file is loaded for secondary