cleanup openh264 build for Android

[alexcohn]

cleaner way to build openh264, not changing the sources at all

includes some files that were missing for arm32 build, as described in #367

This builds smoothly with NDK r21 and NDK r20 on Ubuntu.

[tanersener]

Thanks for the pull request. I have two minor comments.

[tanersener]

Merged to development. Thanks again 👍

I plan to publish a new main release next week. That release will include these changes.

[alexcohn]

BTW, I wanted to ask what was your motivation for efe1c59 ?

[tanersener]

I was using the same host definition in clang -target option and in configure --host= option before this change. But when I was adding support for x86-64-mac-catalyst on iOS, I noticed that some of the configure scripts were failing with the target definition that clang was expecting from me, which was x86_64-apple-ios13.0-macabi. So, I had to use separate values in each of these two. This is the main reason of this change. I applied the same reformatting in Android scripts too. You may find the variable names a little bit misleading but looking from the point that forced me to make this change, it make sense to me.

-target $(get_target_host)

--host=$(get_build_host)