releases/gcc-15 branch: commit r15-9679 failed to bootstrap on Linux/x86_64 (commit builds)!

[haochenj--- via Gcc-testresults]

make[2]: Entering directory '/export/home/haochenj/src/gcc-15-regression'
rm -rf bld
mkdir -p bld
cd bld; \
RUNTESTFLAGS="--target_board='unix{-m32,}'" ../src-15/configure \
        --with-arch=corei7 --with-cpu=corei7 --enable-clocale=gnu 
--with-system-zlib --enable-shared --enable-cet --with-demangler-in-ld 
--enable-libmpx --prefix=/usr/gcc-15.1.1 --with-fpmath=sse 
checking build system type... x86_64-pc-linux-gnu
    grep -E "(error:|Error)" makelog.r15-9679.x86_64.corei7 >> 
makelog.r15-9679.x86_64.corei7.mail; \
    tail -n +20 makelog.r15-9679.x86_64.corei7 | grep -C 10 -E "error:|Error:" 
>> makelog.r15-9679.x86_64.corei7.mail; \
configure:15088: error: possibly undefined macro: AX_PTHREAD
make[6]: *** [Makefile:432: ../../src-15/mpfr/configure] Error 1
make[5]: *** [Makefile:7213: all-stage1-mpfr] Error 2
make[4]: *** [Makefile:29972: stage1-bubble] Error 2
make[3]: *** [Makefile:30373: bootstrap] Error 2
make[2]: *** [Makefile:313: bootstrap] Error 2
==================== Detailed Info around error (+- 10 Lines) 
====================
config.status: creating tests/Makefile
 /bin/sh ./config.status
config.status: creating config.h
config.status: config.h is unchanged
config.status: executing depfiles commands
config.status: executing libtool commands
config.status: executing po-directories commands
config.status: creating po/POTFILES
config.status: creating po/Makefile
(CDPATH="${ZSH_VERSION+.}:" && cd ../../src-15/gettext/gettext-runtime && 
/bin/sh 
'/export/home/haochenj/src/gcc-15-regression/src-15/gettext/build-aux/missing' 
autoheader)
configure:15088: error: possibly undefined macro: AX_PTHREAD
      If this token and others are legitimate, please use m4_pattern_allow.
      See the Autoconf documentation.
make[6]: *** [Makefile:432: ../../src-15/mpfr/configure] Error 1
make[6]: *** Waiting for unfinished jobs....
config.status: creating isl_srcdir.c
config.status: creating Makefile
config.status: creating doc/Makefile
config.status: creating bound_test.sh
config.status: creating codegen_test.sh
config.status: creating pip_test.sh