Add jsr305 as a dependency to AAR.

jsr305 is necessary dependency for Nullable annotations.

Also adds a flag to release_aar.py to specify the build directory
manually. This makes it easier to test the script without full
recompilation.

Bug: webrtc:8881
Change-Id: Ib4b8cd4592ced9c92ca2810928bcbb6173d2164e
Reviewed-on: https://webrtc-review.googlesource.com/65081
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22671}

tools_webrtc/android/templates/pom.jinja

@@ -15,4 +15,12 @@
     <project.build.commitid>{{ commit }}</project.build.commitid>
   </properties>
 
+  <dependencies>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <version>3.+</version>
+    </dependency>
+  </dependencies>
+
 </project>