[android-porting] Adding personal functionality to /external directory

[Lorant Polya]

Hello,

I downloaded and compiled AOSP build OPM1.171019.014 for the Pixel 2 and
the OS works fine on the phone. I want to add a directory under the
/external directory and place my code there. I'm trying to figure out
which makefile I can modify to build my source. I want to create my own
target in the makefile so I can build my code individually or with the rest
of the project. I also want to use libcrypto from boringssl to use sha512
encryption. So I'd like to find the target and makefile that is used to
build libcrypto/boringssl and add that as a dependency to my source.

Regards,
Lorant