glsl: Move glsl_to_nir files to LIBGLSL_FILES
glsl: Move glsl_to_nir files to LIBGLSL_FILES

libglsl_la_SOURCES includes both NIR_FILES and LIBGLSL_FILES, so for
libglsl.la consumers, this is a no-op. libnir.la however no longer uses
any GLSL IR infrastructure and can be used without also linking to
libglsl.la.

Acked-by: Matt Turner <789b315743a28dd066a4ba1459c35951c291d8a6@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler