Add long double test (#492) Required to fix build error on macos with gcc-9
diff --git a/src/x86/ffi64.c b/src/x86/ffi64.c
index 4d53b53..dec331c 100644
--- a/src/x86/ffi64.c
+++ b/src/x86/ffi64.c
@@ -451,9 +451,11 @@ ffi_prep_cif_machdep (ffi_cif *cif)
case FFI_TYPE_DOUBLE:
flags = UNIX64_RET_XMM64;
break;
+#if FFI_TYPE_LONGDOUBLE != FFI_TYPE_DOUBLE
case FFI_TYPE_LONGDOUBLE:
flags = UNIX64_RET_X87;
break;
+#endif
case FFI_TYPE_STRUCT:
n = examine_argument (cif->rtype, classes, 1, &ngpr, &nsse);
if (n == 0)