Add compiler:c11 to USES to fix build on GCC-based systems:
cc1: error: unrecognized command line option "-Wno-unknown-warning-option" cc1: error: unrecognized command line option "-Wsuggest-attribute=noreturn" cc1: error: unrecognized command line option "-Wjump-misses-init" cc1: error: unrecognized command line option "-std=c11"
Approved by: portmgr (tier-2 blanket)