Patch the distfile to include the fix for #2646

See:
https://github.com/bazelbuild/bazel/issues/2646

Recipe:

$ unzip bazel-distfile.zip \
src/java_tools/buildjar/java/com/google/devtools/build/buildjar/VanillaJavaBuilder.java \
src/java_tools/buildjar/javatests/com/google/devtools/build/buildjar/VanillaJavaBuilderTest.java
$ curl \
https://github.com/bazelbuild/bazel/commit/7198fc3a8ffbf096218aa7fc19c71bf7dfa1a1c0.patch \
| patch -p1
$ zip bazel-distfile.zip \
src/java_tools/buildjar/java/com/google/devtools/build/buildjar/VanillaJavaBuilder.java \
src/java_tools/buildjar/javatests/com/google/devtools/build/buildjar/VanillaJavaBuilderTest.java

Change-Id: I05eb0beb420730cef1e325fd4e4a0db7ba324197