spirv: Contain the GLSLang issue #179 workaround to old GLSLang

spirv: Contain the GLSLang issue #179 workaround to old GLSLang

Instead of applying the workaround universally, detect semi-old GLSLang
via the generator ID and only enable the workaround on old GLSLang.
This isn't nearly as precise as one would like it to be because the
first GLSLang generator id version bump was on October 7, 2017 which is
about 1.5 years after the bug was fixed.  However, it at least lets us
disable it for non-GLSLang and for more modern versions.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>