compiler busybox failed (__NR_clock_gettime)

CC libbb/time.o
libbb/time.c: In function `monotonic_us':
libbb/time.c:20: `__NR_clock_gettime' undeclared (first use in this function)
libbb/time.c:20: (Each undeclared identifier is reported only once
libbb/time.c:20: for each function it appears in.)
libbb/time.c:20: `CLOCK_MONOTONIC' undeclared (first use in this function)
libbb/time.c: In function `monotonic_sec':
libbb/time.c:27: `__NR_clock_gettime' undeclared (first use in this function)
libbb/time.c:27: `CLOCK_MONOTONIC' undeclared (first use in this function)
make[1]: *** [libbb/time.o] Error 1


Root cause: uclibc is too old