Due to the division of TU_DEBUG options into runtime and envvar
options, it limited where options could be set from when
TU_DEBUG_FILE was being used. This commit addresses that by allowing
the envvar to set runtime debug options even when TU_DEBUG_FILE is
active while also allowing the file to set non-runtime options if
the file included them at startup.
Signed-off-by: Dhruv Mark Collins <mark@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37580>