Revert workarounds for ThinLTO linker builds.

Revert workarounds for ThinLTO linker builds.

Fixing Issue swiftshader:31 makes the workarounds obsolete and since
they disabled some link-time optimizations they should be reverted.

This reverts commit 628a8496e44ec8a096125cb0cdc3e63bb7dd8380.
This reverts commit 158dcfc13fe3e36217f1bf0d4ccbd8bd80f6d5f1.
This reverts commit ad675fa1d6617ff7fe5965845152ba71f33caf61.

Bug chromium:686980
Bug chromium:735508

Change-Id: I4c4e2466fdfcddd12854b87e5a62d6ec8c823a05
Reviewed-on: https://swiftshader-review.googlesource.com/10168
Reviewed-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Nicolas Capens <capn@google.com>