glsl/standalone: init shader stage in init_gl_program()

Otherwise lima standalone compiler fails when trying to compile fragment
shader with:

lima_compiler: ../src/compiler/nir/nir.c:55: nir_shader_create: Assertion `si->stage == stage' failed

Reviewed-by: Qiang Yu <yuq825@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
1 file changed