c: Fix up expr location for __builtin_stdc_rotate_* [PR118376]

Seems I forgot to set_c_expr_source_range for the __builtin_stdc_rotate_*
case (the other __builtin_stdc_* cases already have it), which means
the locations in expr are uninitialized, sometimes causing ICEs in linemap
code, at other times just valgrind errors about uninitialized var uses.

2025-01-10  Jakub Jelinek  <jakub@redhat.com>

	PR c/118376
	* c-parser.cc (c_parser_postfix_expression): Call
	set_c_expr_source_range before break in the __builtin_stdc_rotate_*
	case.

	* gcc.dg/pr118376.c: New test.