I set CPUTYPE=corei7 in /etc/make.conf, and the value is converted to -march=nehalem by Makefiles installed on FreeBSD 11.0-RELEASE. CentOS 6 uses gcc 4.4 and CentOS 7 uses gcc 4.8, but this option is only supported on gcc >= 4.9, which can cause build failure for devel/linux_libusb. This problem also happens in native FreeBSD gcc (gcc 4.8) and a bug (bug 214173) is already filed for the native port.

===>  Building for linux_libusb-11.0r261448_2
echo libusb.so.3: /usr/lib/libpthread.a >> .depend
Warning: Object directory not changed from original /wrkdirs/usr/ports/devel/linux_libusb/work/linux_libusb-11.0r261448
/compat/linux/usr/bin/gcc  -O2 -pipe -march=corei7  -I/wrkdirs/usr/ports/devel/linux_libusb/work/sys -fstack-protector -fno-strict-aliasing -DCOMPAT_32BIT -DLIBUSB_GLOBAL_INCLUDE_FILE=\"libusb_global_linux.h\" -DUSB_GLOBAL_INCLUDE_FILE=\"libusb_global_linux.h\" -I ../../sys -march=corei7  -MD  -MF.depend.libusb20.o -MTlibusb20.o -std=gnu99 -Wsystem-headers -Werror -Wall -Wno-format-y2k -Wno-uninitialized -Wno-pointer-sign     -c libusb20.c -o libusb20.o
libusb20.c:1: error: bad value (corei7) for -march= switch
libusb20.c:1: error: bad value (corei7) for -mtune= switch
*** Error code 1