CI: add libgcrypt to sanitizer run

Also disable check for unsigned integer overflow.

I couldn't find a way to reliably disable it for a single function:

	https://github.com/google/sanitizers/issues/765

and warnings it produces do not seem to be of enough importance to
introduce ugly hacks like resetting the most significant byte here:

	size_t result = 0;
	// ...

	for(; len; --len) {
		result = (size_t)(result << 8);
		//                      ^^^^