The current Android NDK defines __BIONIC_HAVE_UCONTEXT_T for all
architecures, so the old paths are no longer needed.

Bug: chromium:437330
Change-Id: I6314971e9ee1d78c4b73f8c1b37af7aa6f419b71
Reviewed-on: https://chromium-review.googlesource.com/1252282Reviewed-by: Hannes Payer <hpayer@chromium.org>
Commit-Queue: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56322}