Without libyaml-devel package installed (on Fedora-20),
running ./stack throws:
[. . .]
build/temp.linux-x86_64-2.7/check_libyaml.c:2:18: fatal error: yaml.h:
No such file or directory #include <yaml.h> ^ compilation terminated.
libyaml is not found or a compiler error: forcing --without-libyaml
[. . .]
Adding this dependency to files/rpms/general resolves it. Also added to
files/apts/general.
Change-Id: If1aa23bf3fc76ea2b321c3725dd07050ddd4b825