c: Fix ICEs with -fsanitize=pointer-{subtract,compare} [PR119582]

c: Fix ICEs with -fsanitize=pointer-{subtract,compare} [PR119582]

The following testcase ICEs because c_fully_fold isn't performed on the
arguments of __sanitizer_ptr_{sub,cmp} builtins and so e.g.
C_MAYBE_CONST_EXPR can leak into the gimplifier where it ICEs.

2025-04-02  Jakub Jelinek  <jakub@redhat.com>

	PR c/119582
	* c-typeck.cc (pointer_diff, build_binary_op): Call c_fully_fold on
	__sanitizer_ptr_sub or __sanitizer_ptr_cmp arguments.

	* gcc.dg/asan/pr119582.c: New test.