This is, sadly, not added until CMake 3.4.
This commit avoids continue() by restructuring the loops so
that the conditions previously being used for continue() are
no longer needed. The alternative would've been to encase the
loop bodies massive ifs, but I find that to be a poor choice
for readability.
This requires a macro to override find_package,
as the default behavior in CMake is to fall back
from MODULE onto CONFIG.
Note that Bullet is given a specific override
not to look for a CONFIG, since Bullet tends to
use weird paths in its CONFIG script.
This is preferable because imported targets generally include
all of the relevant information specific to the particular
installation of each package, and without needing to hunt down
a bunch of variables to do it.
To do this, package_option() (which is starting to grow in scope
a little beyond just providing the package option, come to think
of it) is given a new IMPORTED_AS option, which tells the package
configuration system to look for one or more imported targets and
link against them instead.
Instead, let's use a PKG::PKGNAME interface library, which simplifies
the linking and also allows us to use imported libraries from
find_package in the future.
Donny Lawrence
Sam Edwards
kestred