This will make things as std::to_string() and other C++ features
work with a modern and supported C++ library.
We package up libc++_shared.so and bump the revision of every C++
using package to make it rebuild against it.
Users who have built C++ using libraries or programs will probably
need to rebuild them if they are linked against Termux-supplied
libraries, as user code was previously linked against gnustl while
the system libraries are now using libc++, and it's not a good idea
to mix C++ standard libraries in a program.
I put almost 3 hours on this!
It ships with a lot of makefiles for various platforms, notably
one for android_arm. I patched it a bit because Termux already gives
many of the goodies. Probably it could be simplified.
Most of the time went on tinkering with flags and waiting for the
Docker container to reload the new files...there must be a better way!
p7zip doesn't seem to honor $prefix, instead it uses $DEST_HOME.
