How to install libxmlsec1 via Alien::LibXMLSec on Mac OSX

1. Make sure openssl is installed
2. Download Alien::LibXMLSec (it's not on CPAN)
3. Unzip it & change to dir
4. perl Makefile.PL
5. PKG_CONFIG_PATH=/usr/local/Cellar/openssl@1.1/1.1.1k/lib/pkgconfig make
6. make
7. make install

Note: To get the Makefile.PL to run (i.e. step 3½), you may also need to:

• git clone Alien::Build from its git repo
• do a `dzil build` on that
• then set the PERL5LIB to point to the built instance of Alien::Build
• ...and also make sure its deps are in PERL5LIB.