refactor(rez-pip): update the pip install arguments
refactor(rez-pip): update the pip install arguments

Update the pip install arguments to use a specific target directory
to install the requested library. Set the install command to
use PEP 517 for building source distributions to ensure a wheel
is always built before installation.

Relates https://github.com/pypa/pip/pull/4501, https://github.com/nerdvegas/rez/issues/475, https://github.com/nerdvegas/rez/issues/503

instinct-vfx/rez,nerdvegas/rez,instinct-vfx/rez,nerdvegas/rez