glsl: split out libstandalone

Split standalone glsl_compiler into a libstandalone.la and a thin
main.cpp.  This way drivers can re-use the glsl standalone frontend in
their own standalone compilers.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
diff --git a/src/compiler/SConscript.glsl b/src/compiler/SConscript.glsl
index 73abaf1..474df11 100644
--- a/src/compiler/SConscript.glsl
+++ b/src/compiler/SConscript.glsl
@@ -109,6 +109,8 @@
 
 env.Prepend(LIBS = [compiler, glsl])
 
+compiler_objs += env.StaticObject("glsl/main.cpp")
+
 glsl_compiler = env.Program(
     target = 'glsl_compiler',
     source = compiler_objs,