Automatically grabs and compiles libpng, and avoids having hacky lines in our Makefile
(the compiler specification *should* be orthogonal to the build target!)
Also move the MinGW package install to the `install_deps.sh` script,
to move logic off of the YAML.
- Turns out the variable wasn't being set, and thus the flags weren't being passed
- Passing the flags via those variables is basically a bad idea, and it
turns out to break libpng's config script
- The flags need to be passed during link as well, otherwise the binary
isn't linked as a fat one
Besides the immediate performance improvement, reducing
the frequency of downloads should make spurious
failures (network, rate-limiting...) less bothersome.
ISSOtm
vulcandth
Rangi