Handle process_vm_readv availability

Handle the case where process_vm_readv in not availability, given it is gated
on __ANDROID_API__ >= 23 in
third_party/android_toolchain/ndk/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/sys/uio.h

Bug: 375463618
Change-Id: I22764d0d934a6e1e4de5d09def2d51cc16cbed04
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/third_party/libunwindstack/+/6006275
Reviewed-by: Rodney Ding <rodneyding@google.com>
Reviewed-by: Mike Wittman <wittman@chromium.org>
3 files changed