This commit introduces generated overlay filesystem support for
${PATH}, ${LD_LIBRARY_PATH}, and ${PKG_CONFIG_PATH} as well as
includes a working example of how to take advantage of this support
when integrating with vendored code.
FreeBSD does not by default install the Bourne-Again Shell (bash); and
when it is installed, it is most certainly not installed to
``/bin/bash`` due to the nuances of the conventions around local site
packages. Rather, it is installed to ``/usr/local/bin/bash``.
Golang explicitly supports FreeBSD, so it should only be reasonable for
GVM to support this target, too. As a fix, the shell script shebang
definitions now use the ``env`` tool that comes from the _coreutils_
standard package, which is installed on all conventions-adhering Linux
distributions, Mac OS X, and FreeBSD.
FreeBSD prerequisites are now listed in the documentation.
I have tested this against FreeBSD 9.0 release branch on the amd64,
and it works satisfactorily now.