The CL introducing the ESSL 1.0 chunk in materials inadvertently disabled
optimizations for said code. This commit reintroduces those optimizations and
fixes associated bugs which manifested. In particular, spirv-cross was
generating uints for bools; this has been fixed with a hack. Additionally,
spirv-cross is now compiled with exceptions enabled so that matc can gracefully
fail and show the code which failed to compile rather than abruptly aborting.
4116af7971