Toolchain: making android use propagates_configs to enable JNI refactor

We want to depend across toolchains for JNI headers, since they are the
same. This requires a public_config with the correct include_dirs, but
in order for that to propagate across toolchains, we need
propagates_configs.

To test this produces no different compile commands, I ran:

 gn gen out/Test \
 --args='target_os="android" target_cpu="arm64" is_debug=false' && \
 ninja -C out/Test -t commands > /tmp/1 && git checkout HEAD~ && \
 gn gen out/Test && ninja -C out/Test -t commands > /tmp/2 && \
 diff /tmp/1 /tmp/2


Bug: 929682
Change-Id: I56d849a501f3fe59518b5fb7615c13b52f3a894d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4027518
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Sam Maier <smaier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1072235}