-no-opaque-pointers option to Clang to workaround the fact
the Clover code was not ported to opaque pointers yet.
Opaque pointers are now implemented thanks to !19103 (merged) so passing this option to tell Clang to not do opaque pointers while Clover does is actually breaking Clover.
Here is an example of what happens when using opaque pointers while passing -no-opaque-pointers at the same time:
fatal error: cannot open file 'hawaii-amdgcn-mesa-mesa3d.bc': Opaque pointers are only supported in -opaque-pointers mode
This fixes one of the last remaining bits to fully support opaque pointers in Mesa as referenced in #7468, this is the last remaining bit to fully support opaque points in Clover.