build: Cherry-pick libtool.m4 support for GNU ld *_sol2 emulations

build: Cherry-pick libtool.m4 support for GNU ld *_sol2 emulations

GNU ld gained separate Solaris-specific linker emulations (*_sol2) long
ago.  Since their introduction, GCC has preferred them over their
non-*_sol2 counterparts but supported both forms.  This has changed for
GCC 16: since all supported versions of GNU ld do support the *_sol2
emulations, GCC now uses them unconditionally.

libtool has also been updated to handle this since libtool 2.4.2 back in
2011.  However, that change has only partially been backported to the
heavily patched libtool.m4 in the GCC tree: the sparcv9 part is there,
but the amd64 part is missing for some reason.  This causes problems
with some recent binutils changes.

Therefore this patch cherry-picks the libtool patch to bring
Solaris/x86_64 in sync with Solaris/sparcv9 and upstream libtool.

Bootstrapped without regressions on {amd64,i386}-pc-solaris2.11 and
{sparcv9,sparc}-sun-solaris2.11.

2025-09-22  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	* libtool.m4: Cherry-pick libtool commit
	9196966580f6853a31187a7a3c7e7ff36ef08982.

	gcc:
	* configure: Regenerate.

	libatomic:
	* configure: Regenerate.

	libbacktrace:
	* configure: Regenerate.

	libcc1:
	* configure: Regenerate.

	libffi:
	* configure: Regenerate.

	libga68:
	* configure: Regenerate.

	libgcobol:
	* configure: Regenerate.

	libgfortran:
	* configure: Regenerate.

	libgm2:
	* configure: Regenerate.

	libgomp:
	* configure: Regenerate.

	libgrust:
	* configure: Regenerate.

	libitm:
	* configure: Regenerate.

	libobjc:
	* configure: Regenerate.

	libphobos:
	* configure: Regenerate.

	libquadmath:
	* configure: Regenerate.

	libsanitizer:
	* configure: Regenerate.

	libssp:
	* configure: Regenerate.

	libstdc++-v3:
	* configure: Regenerate.

	libvtv:
	* configure: Regenerate.

	lto-plugin:
	* configure: Regenerate.

	zlib:
	* configure: Regenerate.