main/distcc: fix segfault on aarch64
distcc segfaults on aarch64 systems:
# distcc --fds
Segmentation fault (core dumped)Backport upstream patch fixing bad string length calculation in dcc_gcc_rewrite_fqn
Link: https://github.com/distcc/distcc/commit/879b71d6e95673e58d33f6c3c341a893ee307161
master branch version (now merged): !29223 (merged)