gistfile1.txt

$ clang -c -o test test.c -lgmp
clang: warning: -lgmp: 'linker' input unused
test.c:1:10: fatal error: 'gmp.h' file not found
#include <gmp.h>
         ^
1 error generated.

$ clang -I/usr/local/include/ -c -o test test.c -lgmp
clang: warning: -lgmp: 'linker' input unused
test.c:36:3: warning: implicit declaration of function '__gmpz_out_str' is invalid in C99 [-Wimplicit-function-declaration]
  mpz_out_str(stdout,10,n);
  ^
/usr/local/include/gmp.h:960:21: note: expanded from macro 'mpz_out_str'
#define mpz_out_str __gmpz_out_str
                    ^
1 warning generated.