Add prebuilts/checkstyle dependency to master branch.

checkstyle.jar was living in development/tools/checkstyle
which is not a good place for a prebuilt. This CL adds dependency
to the 6MB repo of prebuilts/checkstyle to master.
Bug: 33666900
Change-Id: Ia76762052d73372c4aea684c455c228ea81fbc6b

default.xml

@@ -485,6 +485,7 @@
   <project path="platform_testing" name="platform/platform_testing" groups="pdk-fs,pdk-cw-fs,cts" />
   <project path="prebuilts/android-emulator" name="platform/prebuilts/android-emulator" groups="pdk-fs" clone-depth="1" />
   <project path="prebuilts/build-tools" name="platform/prebuilts/build-tools" groups="pdk" clone-depth="1" />
+  <project path="prebuilts/checkstyle" name="platform/prebuilts/checkstyle" groups="pdk" clone-depth="1" />
   <project path="prebuilts/clang/host/darwin-x86" name="platform/prebuilts/clang/host/darwin-x86" groups="pdk,darwin" clone-depth="1" />
   <project path="prebuilts/clang/host/linux-x86" name="platform/prebuilts/clang/host/linux-x86" groups="pdk" clone-depth="1" />
   <project path="prebuilts/deqp" name="platform/prebuilts/deqp" groups="pdk-fs" clone-depth="1" />