This is an update to the package to address to FTBFs issue on armel. The
package has been newly introduced to Trixie from unstable where the
issue did not occur since there is no armel.

As a test I built the resulting package on Amdahl (the armel porterbox).

The change is limited to to armel architecture so it won't have an
affect other architectures such as amd64 or even armhf.

The build of the package aborts because a symbol, which is asked for by
libstdc++-14-dev (gcc-14) is not provided during the linking stage.
That symbol is is conditionally provided depending on compiler define.
gcc's define (for ATOMIC_INT_LOCK_FREE) is different than llvm's. As a
result gcc has a different version of the code where the symbol is not
compiled and provided while llvm expects that symbol.
The workaround is to align the define on llvm to match gcc's expectation
since armel in general has no (or different) atomic support (the SoCs at
that time were usually UP).
One thing that is not perfect: if clang is used to cross compile (i.e.
create armel code on amd64 or amd64 code on armel) then the define will
be wrong.

Sebastian