Auto-sync with upstream branch master
    
    Upstream commit: ef7f4b1fef67430a8f3cfc77fa6aada2add851d7
    
    - Apply the Makefile sorting fix
    - sysdeps/x86_64/Makefile (tests): Add the end marker
    - sort-makefile-lines.py: Allow '_' in name and "^# name"
    - trivial doc fix: remove weird phrase "syscall takes zero to five arguments"
    - mips: Use builtins for ffs and ffsll
    - x86: Expand the comment on when REP STOSB is used on memset
    - x86: Do not prefer ERMS for memset on Zen3+
    - x86: Fix Zen3/Zen4 ERMS selection (BZ 30994)
    - x86/cet: fix shadow stack test scripts
    - test_printers_common.py: Remove invalid escape sequence
    - elf: Remove attempt at env handling in elf/tst-rtld-list-diagnostics.py
    - Add SOL_VSOCK from Linux 6.7 to bits/socket.h
    - localedata: ssy_ER: Fix syntax error
    - localedata: hr_HR: change currency to EUR/€
    - Change lv_LV collation to agree with the recent change in CLDR
    - Add new AArch64 HWCAP2 definitions from Linux 6.7 to bits/hwcap.h
    - string: Add hidden builtin definition for __strcpy_chk.
    - arm: Remove wrong ldr from _dl_start_user (BZ 31339)
    - LoongArch: Use builtins for ffs and ffsll
    - Remove sysdeps/ia64/math-use-builtins-ffs.h
    - Fix stringop-overflow warning in tst-strlcat2.
    - mips: FIx clone3 implementation (BZ 31325)
    - stdlib: fix qsort example in manual
    - soft-fp: Add brain format support
    - Rename c2x / gnu2x tests to c23 / gnu23
    - manual: Fix up stdbit.texi
    - string: Use builtins for ffs and ffsll
    - misc: tst-poll: Proper synchronize with child before sending the signal
    - math: Remove bogus math implementations
    - Refer to C23 in place of C2X in glibc
    - elf: Remove _dl_sysdep_open_object hook function
    - build-many-glibcs: relax version check to allow non-digit characters
    - Use gcc __builtin_stdc_* builtins in stdbit.h if possible
    - Open master branch for glibc 2.40 development