ipa: Initialize/release global obstack in process_new_functions [PR116068]

Other spots in cgraphunit.cc already call bitmap_obstack_initialize (NULL);
before running a pass list and bitmap_obstack_release (NULL); after that,
while process_new_functions wasn't doing that and with the new r15-130
bitmap_alloc checking that results in ICE.

2025-01-15  Jakub Jelinek  <jakub@redhat.com>

	PR ipa/116068
	* cgraphunit.cc (symbol_table::process_new_functions): Call
	bitmap_obstack_initialize (NULL); and bitmap_obstack_release (NULL)
	around processing the functions.

	* gcc.dg/graphite/pr116068.c: New test.