[gdb/testsuite] Handle removed valgrind option --db-attach

When running valgrind-db-attach.exp with valgrind version 3.13.0, we get:
...
PASS: gdb.base/valgrind-db-attach.exp: spawn valgrind
valgrind: Unknown option: --db-attach=yes
valgrind: Use --help for more information or consult the user manual.
ERROR: Process no longer exists
UNRESOLVED: gdb.base/valgrind-db-attach.exp: valgrind started
...

The valgrind option --db-attach has been deprecated in version 3.10.0, and
removed in version 3.11.0.

Fix valgrind-db-attach.exp to replace the ERROR/UNRESOLVED with:
...
UNSUPPORTED: gdb.base/valgrind-db-attach.exp: valgrind started
...

Tested on x86_64-linux.

2018-10-24  Tom de Vries  <tdevries@suse.de>

	* gdb.base/valgrind-db-attach.exp: Handle removed support for
	--db-attach in valgrind.

1 files changed, 4 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/valgrind-db-attach.exp b/gdb/testsuite/gdb.base/valgrind-db-attach.exp
index 3be6af5ca94..3e40283a955 100644
--- a/gdb/testsuite/gdb.base/valgrind-db-attach.exp
+++ b/gdb/testsuite/gdb.base/valgrind-db-attach.exp
@@ -51,6 +51,10 @@ set use_gdb_stub 1
 set test "valgrind started"
 # The trailing '.' differs for different memcheck versions.
 gdb_test_multiple "" $test {
+    -re "valgrind: Unknown option: --db-attach=yes" {
+	unsupported $test
+	return -1
+    }
     -re "Memcheck, a memory error detector\\.?\r\n" {
 	pass $test
     }