re PR go/90614 (gcc-9.1.0/libgo/go/syscall/wait.c:54:22: error: unused parameter ‘w’ [-Werror=unused-parameter] Continued (uint32_t *w))

	PR go/90614
    syscall: avoid unused parameter error if WIFCONTINUED not defined
    
    Fixes https://gcc.gnu.org/PR90614
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/178997

From-SVN: r271638