[committed] Fix sysdeps/mips/dl-machine-reject-phdr.h build with GCC 16

[Joseph Myers]

Building for MIPS has been broken with GCC mainline since mid-July,
probably GCC commit 0eac9cfee8cb0b21de866a04d5d59685ab35208f "c, c++:
Extend -Wunused-but-set-* warnings [PR44677]", because the variable
perfect_match in elf_machine_reject_phdr_p is set unconditionally, but
only used if _MIPS_SIM == _ABIO32.  Mark it with __attribute__ ((unused)),
which seems cleaner in such a conditionally-used case than making all
other logic relating to this variable conditional.

Tested with build-many-glibcs.py (compilers build, which previously
failed) for mips64-linux-gnu.

diff --git a/sysdeps/mips/dl-machine-reject-phdr.h b/sysdeps/mips/dl-machine-reject-phdr.h
index 72bb9087a8..46852d241f 100644
--- a/sysdeps/mips/dl-machine-reject-phdr.h
+++ b/sysdeps/mips/dl-machine-reject-phdr.h
@@ -162,7 +162,7 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
   int in_abi = -1;
   struct abi_req in_req;
   Elf_MIPS_ABIFlags_v0 mips_abiflags;
-  bool perfect_match = false;
+  bool perfect_match __attribute__ ((unused)) = false;
 #if _MIPS_SIM == _ABIO32
   unsigned int cur_mode = -1;
 # if HAVE_PRCTL_FP_MODE

-- 
Joseph S. Myers
josmyers@redhat.com