tests: Ignore test executables

Commits 9ef8112a and efad6682 introduced new tests, but forgot
to ignore the built executables from an in-tree build.
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

tests/.gitignore

@@ -12,7 +12,9 @@ rcutorture
 test-aio
 test-base64
 test-bitops
+test-blockjob
 test-blockjob-txn
+test-bufferiszero
 test-clone-visitor
 test-coroutine
 test-crypto-afsplit