Add new items to gitignore.

- binutils - downloaded and decompressed package artifacts
- protobuf generated sources
- *.class files, which are java compile artifacts.

The protobuf and *.class artifacts are here as work-arounds for jdt.ls
(vscode, vim, ...) plugin generating these files in the source tree upon
import.

Change-Id: I111a6549a3c750dec4cadfda7a3a2bf429ac0110
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2218865
Commit-Queue: Ender <ender@google.com>
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773457}

.gitignore

@@ -46,6 +46,7 @@
 .project
 .pydevproject
 .checkstyle
+*.class
 compile_commands.json
 cscope.*
 GPATH

third_party/.gitignore

@@ -40,6 +40,7 @@
 /arcore-android-sdk/test-apks/arcore/*.apk
 /asan
 /bazel/desugar/*.jar
+/binutils
 /bison
 /boringssl/src
 /bouncycastle/lib/
@@ -179,6 +180,7 @@
 /perl
 /ppapi
 /proguard/lib/
+/protobuf/java/lite/target/
 /protoc_javalite/protoc-gen-javalite
 /psyco_win32
 /pthreads-win32