gprofng: fix regression in testing for not yet installed version

gprofng/ChangeLog
2022-07-07  Vladimir Mezentsev  <vladimir.mezentsev@oracle.com>

	* src/Settings.cc (Settings::read_rc): Read environment variable
	GPROFNG_SYSCONFDIR.
	* testsuite/lib/Makefile.skel: Export GPROFNG_SYSCONFDIR.
	* testsuite/gprofng.display/display.exp: Shorten the list of tests.