I've tested and both "-fno-pie" and "-static" are not compatible with some gcc and clang sanitizers, so these solutions are bad.
Found right solution in gmp source. It was hidden in configure: "--with-pic" option. I've enabled it and now both glibc and musl works perfect. Created gentoo bug
https://bugs.gentoo.org/707332. For everyone who will read this thread - you need to enable "--with-pic" option for gmp. You don't need to disable assembly completely.
So on this week I will try to create small user friendly patch for musl about readonly relocations.