config.sub: recognize *-*-uefi

This commit causes gnu-config to recognize the *-*-uefi triples.

These triples describe binaries which use the PE object file format
and UEFI calling "convention" (which is actually a family of
completely unrelated calling conventions, one per CPU architecture):

- https://uefi.org/specs/UEFI/2.9_A/02_Overview.html#detailed-calling-convention
- https://uefi.org/specs/UEFI/2.9_A/02_Overview.html#detailed-calling-convention-1
- https://uefi.org/specs/UEFI/2.9_A/02_Overview.html#detailed-calling-convention-2
- https://wiki.osdev.org/UEFI#Calling_Conventions

This is in contrast to the *-w64-mingw32 triple of GNU-EFI, which
uses the ELF format and cdecl calling convention:

- https://wiki.osdev.org/UEFI#Calling_Conventions

Because *-*-uefi uses a different object file format (everywhere)
and calling convention (everywhere except x86_32) from
*-w64-mingw32, the resulting binaries cannot be linked against each
other.  This is the primary justification for introducing a new
triple.

Since gnu-config does not yet have triples for these builds, we
might as well use the same ones already selected by LLVM.  It
considers uefi to be an operating system:

- https://reviews.llvm.org/D131594

* config.sub (*-*-uefi): Recognize.
* testsuite/config-sub.data (i686-unknown-uefi, x86_64-unknown-uefi,
  aarch64-unknown-uefi): New entries.

Signed-off-by: Adam Joseph <adam@westernsemico.com>
X-Disclaimer: This commit shall not be construed as the author's approval of the UEFI boondoggle in any way, shape or form.
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>

config.sub

@@ -4,7 +4,7 @@
 
 # shellcheck disable=SC2006,SC2268 # see below for rationale
 
-timestamp='2023-10-28'
+timestamp='2023-10-29'
 
 # This file is free software; you can redistribute it and/or modify it
 # under the terms of the GNU General Public License as published by
@@ -1773,6 +1773,13 @@ case $os in
 	sco3.2v2 | sco3.2v[4-9]* | sco5v6*)
 		# Don't forget version if it is 3.2v4 or newer.
 		;;
+	# This refers to builds using the UEFI calling convention
+	# (which depends on the architecture) and PE file format.
+	# Note that this is both a different calling convention and
+	# different file format than that of GNU-EFI
+	# (x86_64-w64-mingw32).
+	uefi)
+		;;
 	none)
 		;;
 	kernel* | msvc* )