[gdb/testsuite] Add comment in gdb.base/vla-optimized-out.c

2018-07-26  Tom de Vries  <tdevries@suse.de>

	* gdb.base/vla-optimized-out.c: Add comment about origin of test-case.

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2018-07-26  Tom de Vries  <tdevries@suse.de>
+
+	* gdb.base/vla-optimized-out.c: Add comment about origin of test-case.
+
 2018-07-26  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.base/maint.exp: Add check that dwarf unwinders control flag

gdb/testsuite/gdb.base/vla-optimized-out.c

@@ -15,6 +15,9 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+/* The version of this test-case with f1 tagged with noinline only is equivalent
+   to gcc/testsuite/gcc.dg/guality/vla-1.c.  */
+
 int
 #ifdef NOCLONE
 __attribute__((noinline, noclone))