I've found out that when GCC (tried on GCC 4.8 and GCC 6.4) finds real-ld executable in its search path, it is silently ignoring -fuse-ld=... option, and use real-ld instead of appropriate linker.
$ echo "int main(){}" > script.c
$ ln -s /usr/bin/ld real-ld
$ gcc -fuse-ld=gold -B$PWD script.c
$ readelf --string-dump=.note.gnu.gold-version a.out
readelf: a.out: Warning: Section '.note.gnu.gold-version' was not dumped because it does not exist!
Normally, without real-ld it will work as expected:
$ echo "int main(){}" > script.c
$ gcc -fuse-ld=gold script.c
$ readelf --string-dump=.note.gnu.gold-version a.out
String dump of section '.note.gnu.gold-version':
[ c] GNU
[ 10] gold 1.12
Documentation of GCC suggests that gold linker will be used.
Documentation of collect2 does not say anything about -fuse-ld feature...