ImageMagick 6.x compile error on centos 6

I ran into some problems updating image magick on older centos6 systems. Specifically ImageMagick-6.9.10-50 which would error during the make compile with:

magick/.libs/libMagickCore-6.Q16.so: undefined reference to `clock_gettime'
collect2: ld returned 1 exit status
make[1]: *** [utilities/animate] Error 1
make[1]: Leaving directory `/usr/src/ImageMagick-6.9.10-50'
make: *** [all] Error 2

This can be fixed by adding compile time flags:

LDFLAGS=" -lrt " ./configure
LDFLAGS=" -lrt " make