Revert r295944.

Even though the change works perfectly fine on CloudABI, it fails to
work on the libcxx-libcxxabi-libunwind-arm-linux-noexceptions build bot.
Looking at the code, this may be attributed to the fact that the code
doesn't take the PT_LOAD addresses into consideration.

I will rework this change to fix that and send out an updated version
for review in the nearby future.

llvm-svn: 295948