Build error on x86_64

[Roland McGrath]

> I recently got the following error building ufsparse on x86_64 for 
> development:
> 
> + make -f Makefile 'CFLAGS=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=nocona -fPIC' libldl.a
> gcc -c -O ldl.c -o ldl.o

There is no -fPIC here.  Perhaps the makefile doesn't use CFLAGS?