gimple-fold: Preserve location in gimple_fold_builtin_memset

gimple-fold: Preserve location in gimple_fold_builtin_memset

As mentioned yesterday, gimple_fold_builtin_memset doesn't preserve
locus which means e.g. the -Wstringop-overflow warnings are emitted as:
In function 'test_max':
cc1: warning: writing 1 byte into a region of size 0 [-Wstringop-overflow=]
The function emits up to 2 new statements, but the latter (asgn) is added
through gsi_replace and therefore the locus is copied over from the call.
But store is emitted before the call and optionally the call removed
afterwards, so locus needs to be copied over manually.

2021-10-29  Jakub Jelinek  <jakub@redhat.com>

	* gimple-fold.c (gimple_fold_builtin_memset): Copy over location from
	call to store.

	* gcc.dg/Wstringop-overflow-62.c: Adjust expected diagnostics.