Compile apps from github source on device via termux or apps? Is there any app's like "apk builder" by heagoo that can compile apks on device from github source? 

Termux method would be nice too if anyone knows. 
I have tried "sdrausty.github.io" method but I believe that's more for his pre-configured apks. I want something more universal.

Specifically, I'm looking to build this app: https://github.com/ukanth/afwall
any app's ... that can compile apks on device from github source?

The command ~/buildAPKs/build.github.bash can build nearly an unlimited number of APKs which are available at GitHub today and is available at https://github.com/BuildAPKs/buildAPKs.
This BASH script uses aapt, ecj, dx and apksigner in Termux and Termux PRoot to make APKs on device and runs in Amazon, Android, Arch Linux, Debian, Chromebook, Ubuntu and Windows.
The https://github.com/BuildAPKs/db.BuildAPKs repository has build results for a few of the accounts at GitHub.  For example, the B10NAMES file has GitHub login names that built at least 10 APKs on device in Termux.

Specifically, I'm looking to build this app: https://github.com/ukanth/afwall

$ ~/buildAPKs/build.github.bash https://github.com/ukanth/
build.github.bash: Beginning BuildAPKs with build.github.bash https://github.com/ukanth/:
.
.
.
Results for ukanth: 
com.ukanth.simplebatterytemp.apk
com.andraskindler.quickscroll.apk
com.stericson.RootShell.apk

The app afwall does not build on the fly with BuildAPKs at present.  Three of ukanth's apps do build on device in Termux on Android out of box.  With modifications to this script, afwall should also build on device today.