Bug#1131804: gcc-14-cross-ports: FTBFS: libgnat-14.so: undefined reference to `__atomic_compare_exchange_8'

Package: src:gcc-14-cross-ports
Version: 14
Severity: serious
Tags: ftbfs forky sid

Dear maintainer:

During a rebuild of all packages in unstable, this package failed to build.

Below you will find the relevant part of the build log. If required,
the full build log is available here:

https://people.debian.org/~sanvila/build-logs/202603/

About the archive rebuild: The build was made on virtual machines from AWS,
using sbuild and a reduced chroot with only build-essential packages.

If you cannot reproduce the bug please contact me privately, as I
am willing to provide ssh access to a virtual machine where the bug is
fully reproducible.

If this is really a bug in one of the build-depends, please use
reassign and add an affects on src:gcc-14-cross-ports, so that this is still
visible in the BTS web page for this package.

Thanks.

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[...]
cd rts; /<<PKGBUILDDIR>>/gcc/build/./gcc/xgcc -B/<<PKGBUILDDIR>>/gcc/build/./gcc/ -B/usr/arm-linux-gnueabi/bin/ -B/usr
/arm-linux-gnueabi/lib/ -isystem /usr/arm-linux-gnueabi/include -isystem /usr/arm-linux-gnueabi/sys-include -isystem /
<<PKGBUILDDIR>>/gcc/build/sys-include    -shared -g -O2  \
        -fPIC \
        -o libgnarl-14.so \
        -Wl,-z,relro -Wl,--no-allow-shlib-undefined -Wl,--no-copy-dt-needed-entries -Wl,--no-undefined \
        a-dispat.o a-dynpri.o a-interr.o a-intnam.o a-reatim.o a-retide.o a-rttiev.o a-synbar.o a-sytaco.o a-tasatt.o 
a-taside.o a-tasini.o a-taster.o g-boubuf.o g-boumai.o g-semaph.o g-signal.o g-tastus.o g-thread.o s-inmaop.o s-interr
.o s-intman.o s-mudido.o s-osinte.o s-proinf.o s-putaim.o s-solita.o s-stusta.o s-taasde.o s-tadeca.o s-tadert.o s-tae
nca.o s-taprob.o s-taprop.o s-tarest.o s-tasdeb.o s-tasinf.o s-tasini.o s-taskin.o s-taspri.o s-tasque.o s-tasren.o s-
tasres.o s-tassta.o s-tasuti.o s-tataat.o s-tpinop.o s-tpoben.o s-tpobop.o s-tposen.o thread.o s-linux.o \
        -Wl,-soname,libgnarl-14.so \
        libgnat-14.so \
        -ldl \
        -lpthread
/usr/bin/arm-linux-gnueabi-ld.bfd: libgnat-14.so: undefined reference to `__atomic_compare_exchange_8'
/usr/bin/arm-linux-gnueabi-ld.bfd: libgnat-14.so: undefined reference to `__atomic_load_8'
collect2: error: ld returned 1 exit status
make[8]: *** [gcc-interface/Makefile:689: gnatlib-shared-default] Error 1
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