asahi/clc: remap __FILE__

important for reproducability. wondering if we can do this in common code but
not sure how yet.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Mary Guillemard <mary.guillemard@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32529>

src/asahi/libagx/meson.build

@@ -16,6 +16,11 @@ prepended_input_args = []
 foreach input_arg : libagx_shader_files
   prepended_input_args += ['--in', input_arg]
 endforeach
+
+# We need to set -fmacro-prefix-map properly for reproducability.
+fs = import('fs')
+relative_dir = fs.relative_to(meson.global_source_root(), meson.global_build_root()) + '/'
+
 libagx_spv = custom_target(
   'libagx.spv',
   input : libagx_shader_files,
@@ -28,6 +33,7 @@ libagx_spv = custom_target(
     '-I' + join_paths(meson.current_source_dir(), '../../'),
     '-I' + join_paths(meson.current_source_dir(), 'shaders'),
     '-I' + join_paths(meson.current_build_dir(), '../genxml'),
+    '-fmacro-prefix-map=@0@='.format(relative_dir),
     ],
   env: ['MESA_SHADER_CACHE_DISABLE=true'],
   depends : [prog_mesa_clc, agx_pack],