libwebp.jar: build w/Java 1.6 for Android compat

broken since:
 a5c297c swig/java: reduce wrapper function code duplication

this was a part of v0.3.1, but not v0.3.0.

Change-Id: I001d4bd0a7a1aa1b2d267bc63bc1d8226bff00c1
(cherry picked from commit de899516c752faab0bfe87eb6614e7960022809f)
1 file changed