Darwin, configure: Allow for an unrecognisable dsymutil [PR111610].

Darwin, configure: Allow for an unrecognisable dsymutil [PR111610].

We had a catch-all configuration case for missing or unrecognised dsymutil
but it was setting the dsymutil source to "UNKNOWN" which is not usable in
this context (since it clashes with an existing enum).  We rename this to
DET_UNKNOWN (for Darwin External Toolchain).

	PR target/111610

gcc/ChangeLog:

	* configure: Regenerate.
	* configure.ac: Rename the missing dsymutil case to "DET_UNKNOWN".

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>