build: Fix up spirv_info.Plo

build: Fix up spirv_info.Plo

spirv_info.c existed as a static file until commit 2dd4e2ece32f began
generating it as part of the build process. autotools is incapable of
coping, and so a build-tree from before this commit would then fail with
it:

[4]: *** No rule to make target '../../../mesa/src/compiler/spirv/spirv_info.c', needed by 'spirv/spirv_info.lo'.  Stop.

Add a few lines to configure.ac to update the broken build files.

Reviewed-by: Emil Velikov <emil.velikov@collabora.com>