Switch from libgcc to compiler-rt

[joakim-noah]

Since the NDK has switched to clang, surely it would be better for Termux to use compiler-rt instead? Maybe it's worth trying to compile several packages with compiler-rt and see if anything breaks.

[alive4ever]

#72 has some information regarding libgcc and compiler-rt

[fornwall]

Note that the NDK hasn't switched to compiler-rt yet (but probably plans to): android/ndk#294

The easiest way would be to wait for the NDK to start using compiler-rt and use it in Termux, just like libgcc is now, but for now we could look into packaging it ourselves.

[DanAlbert]

You can probably close this. This isn't a detail that NDK users should have to think about. We'll make the switch inside the NDK and it will make its way downstream to you.

[joakim-noah]

We've already switched to libc++ too, so Termux precedes the NDK. At the very least, we could provide an optional compiler-rt package, that users could choose to rely on in place of the libgcc package that clang automatically pulls in.