lang/gcc15-devel: Fix SIGBUS depending on CPUTYPE

Compiling GCC with some CPUTYPE values (e.g. broadwell) result in
breaking some applications (e.g. math/octave, cad/freecad), sending
a SIGBUS.

The issue is due to GCC generating instructions that require
variables
to be aligned in memory on certain CPUs. Our libthr does not have
the
required alignment so these CPUs fail to execute these instructions.

The patch disables the generation of such instructions.

PR: 285711
Reported by: cracauer
Tested by: cracauer, jbo