Update gitignore for Cargo.lock and tags

Bug: 176847216
Tag: #floss
Test: atest --host bluetooth_test_gd

Change-Id: I3ccf85d54493630257957a1c5182e54470bcb16f
diff --git a/.gitignore b/.gitignore
index 92b837b..5acc85a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,6 @@
 buildtools
 out
-third_party
+third_party/
+target/
+Cargo.lock
+tags