tests: Ignore more test executables

Ignore test executables when building in-tree:
test-arm-mptimer introduced in commit 882fac3
test-crypto-hmac introduced in commit 4fd460b
test-aio-multithread introduced in commit 0c330a7

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

tests/.gitignore

@@ -11,6 +11,8 @@ check-qom-proplist
 qht-bench
 rcutorture
 test-aio
+test-aio-multithread
+test-arm-mptimer
 test-base64
 test-bitops
 test-bitcnt
@@ -24,6 +26,7 @@ test-crypto-afsplit
 test-crypto-block
 test-crypto-cipher
 test-crypto-hash
+test-crypto-hmac
 test-crypto-ivgen
 test-crypto-pbkdf
 test-crypto-secret