The problem is described here.
There have been patches for 1.8, JRuby and later version of ree, but I can't find anything for this version.
I tried applying this patch.
But compiling fails with an error that doesn't make sense since there are no changes to the compiler directives that I can see:
gcc -g -Os -fno-strict-aliasing -DRUBY_EXPORT -D_GNU_SOURCE=1 -I. -I. -c st.c
st.c:230:49: error: '#' is not followed by a macro parameter
make: *** [st.o] Error 1