Switch from GNU to LLVM based tools.

Android NDK 23 switched to a LLVM based toolchain. However some LLVM
based tools like llvm-readobj and llvm-objcopy are available with NDK 22
already. To prepare the roll to NDK 23, switch to llvm-readobj and
llvm-copy for Android builds.

Bug: 1246049
Change-Id: I1cc3cec4aeaa159f6189f810ff6e709879b51204
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3162163


Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Richard Townsend <richard.townsend@arm.com>
Cr-Commit-Position: refs/heads/main@{#922566}