Reland "Disable lld for ARM versions older than 7." and "Switch the default linker to lld on Android."

This relands commits 7b895661b955a3ae520a83eec7f1b3db282ddbc0 and
2ca66ef8ae32044a7ec9ea40ad1d9ee4ae295be1 which were reverted in commit
7450c138da28094f40dcd8da177ac1d643018da8.

> Switch the default linker to lld on Android.
>
> All known blockers have now been fixed. This CL is likely to uncover
> unknown blockers, and is a likely culprit for any issues involving
> crash dumping or symbolization on Android.
>
> MIPS is excluded because of an incompatibility between Android MIPS
> prebuilts and lld (https://github.com/android-ndk/ndk/issues/617).

> Disable lld for ARM versions older than 7.
>
> lld currently does not support ARMv<7.

Bug: 742655
Change-Id: I3f8848fad91f9132288fe7b704c74cd58f8e5eae
Reviewed-on: https://chromium-review.googlesource.com/879346
Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Peter Collingbourne <pcc@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#531064}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 19466659246a1ae1a77760fc241a868da6c57020

config/compiler/compiler.gni

@@ -159,7 +159,9 @@ declare_args() {
   use_lld = is_clang && !is_msan &&
             ((is_win && host_os != "win") || is_fuchsia ||
              (use_thin_lto && target_os != "chromeos") ||
-             (is_linux && current_cpu == "x64" && target_os != "chromeos"))
+             (is_linux && current_cpu == "x64" && target_os != "chromeos") ||
+             (is_android && (current_cpu != "arm" || arm_version >= 7) &&
+              current_cpu != "mipsel" && current_cpu != "mips64el"))
 }
 
 declare_args() {