Set java_version:1.8 for Android stubs jar generation

Currently Soong based Android stubs jar generation is broken
when EXPERIMENTAL_USE_OPENJDK9=true with following errors:
"Unable to find package java.lang in classpath or bootclasspath"

In old development/build/build_android_stubs.mk
all these jar targets were forced to be built with -source 1.8 -target
1.8
https://android-review.googlesource.com/c/platform/development/+/630280

Test: m android_stubs_current EXPERIMENTAL_USE_OPENJDK9=true
Bug: b/70351683

Change-Id: Ice0224a97e458f92e5b4c5994fa67079d2788d57
1 file changed