GSoC: Separation of Ports Build Process from Local Installation

[Theron Tarigo]

Hello all,

My progress this past week has been the following:
- Familiarized myself with the port dependency mechanisms in 
/usr/ports/Mk/Scripts.
- Hacked on bsd.port.mk to check assumptions and to get an idea of what 
additions will be needed.
- Studied /usr/src/lib/libc to understand chain of userspace calls 
between C API and system call. Implemented proof-of-concept redirection 
library intercepting open(...).

This progress so far is on schedule according to my timeline at 
https://wiki.freebsd.org/SummerOfCode2019Projects/PortsSeparatedBuild .

Theron Tarigo