fix Debian testing GCC job

GNU Gold Linker is going away, so we need to remove "-Wl,-fuse-ld=gold" from LDFLAGS

see https://packages.debian.org/sid/binutils-gold "WARNING: gold is being removed from binutils, and is deprecated upstream."

and https://lists.gnu.org/archive/html/info-gnu/2025-02/msg00001.html