contrib: change gmp download url for mac silicon

This commit uses latest gmp version since it fixes
build for arm64 for macOS with assembly enabled.

It does not fix the build for iPhone, so the
option --disable-assembly should still be used when
building for iOS.

Change-Id: I045e0372c36367f22f8b8a95aaac987e559c6d02

contrib/src/gmp/SHA512SUMS

 8904334a3bcc5c896ececabc75cda9dec642e401fb5397c4992c4fabea5e962c9ce8bd44e8e4233c34e55c8010cc28db0545f5f750cbdbb5f00af538dc763be9  gmp-6.2.1.tar.bz2
+e16b5b46d66872270e6987318172c3457ba008e4f21c7622e774b418769dd9a3a9a4521d4bfc61de239e55c5f810c057ec9dacc01a42dbece064d8c5c9a2650a  gmp-6.2.99-20221117121717.tar.bz2

contrib/src/gmp/rules.mak

 # GNU Multiple Precision Arithmetic
 
+
+ifdef HAVE_MACOSX
+ifeq ($(ARCH),arm64)
+GMP_VERSION := 6.2.99-20221117121717
+GMP_URL := https://gmplib.org/download/snapshot/gmp-next/gmp-$(GMP_VERSION).tar.zst
+else
+GMP_VERSION := 6.2.1
+GMP_URL := $(GNU)/gmp/gmp-$(GMP_VERSION).tar.bz2
+endif
+else
 GMP_VERSION := 6.2.1
 GMP_URL := $(GNU)/gmp/gmp-$(GMP_VERSION).tar.bz2
+endif
 
 $(TARBALLS)/gmp-$(GMP_VERSION).tar.bz2:
 	$(call download,$(GMP_URL))