intel/compiler: Add brw_get_compiler_config_value for disk cache

During code review, Jason pointed out that:

2b3064c073 "i965, anv: Use INTEL_DEBUG for disk_cache driver flags"

Didn't account for INTEL_SCALER_* environment variables.

To fix this, let the compiler return the disk_cache driver flags.

Another possible fix would be to pull the INTEL_SCALER_* into
INTEL_DEBUG bits, but as we are currently using 41 of 64 bits, I
didn't think it was a good use of 4 more of these bits. (5 since
INTEL_PRECISE_TRIG needs to be accounted for as well.)

Cc: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/intel/compiler/brw_compiler.h

@@ -1214,6 +1214,18 @@ DEFINE_PROG_DATA_DOWNCAST(sf)
 struct brw_compiler *
 brw_compiler_create(void *mem_ctx, const struct gen_device_info *devinfo);
 
+/**
+ * Returns a compiler configuration for use with disk shader cache
+ *
+ * This value only needs to change for settings that can cause different
+ * program generation between two runs on the same hardware.
+ *
+ * For example, it doesn't need to be different for gen 8 and gen 9 hardware,
+ * but it does need to be different if INTEL_DEBUG=nocompact is or isn't used.
+ */
+uint64_t
+brw_get_compiler_config_value(const struct brw_compiler *compiler);
+
 unsigned
 brw_prog_data_size(gl_shader_stage stage);