ext/ffi: Pass $FFI_LIBS to PHP_CHECK_LIBRARY to fix shared builds

Author: hughmcmaster

ext/ffi/config.m4

@@ -15,6 +15,8 @@ if test "$PHP_FFI" != "no"; then
     AC_DEFINE(HAVE_FFI,1,[ Have ffi support ])
   ], [
     AC_MSG_ERROR(FFI module requires libffi)
+  ], [
+    $FFI_LIBS
   ])
 
   AC_CACHE_CHECK([for fastcall calling convention], ac_cv_ffi_fastcall,