In commit 9d9dd861e9 ("[gdb/testsuite] Fix regression in
step-indirect-call-thunk.exp with gcc 7") I accidentally committed a duplicate
of supports_gnuc, which caused:
...
DUPLICATE: gdb.base/gdb-caching-proc.exp: supports_gnuc: consistency
...
Fix this by removing the duplicate.
Tested on x86_64-linux.