CMake supports a number of strings for truthy and falsey values.
ON/OFF and TRUE/FALSE are the most popular but 1/0 is also supported.
This is mostly a style choice but I'm inclined to believe that ON/OFF
is the most popular option and I'm generally in favor of style
choices that better align with the community at large.
This is the warning I got when building this locally
ld: warning: ignoring duplicate libraries: 'lib/libsfml-graphics-s-d.a', 'lib/libsfml-system-s-d.a', 'lib/libsfml-window-s-d.a'
CMake doesn't require absolute paths so we can safely remove
SRCROOT and let implicit relative pathing achieve the same result
with less work on our part.
This removes the sfml- prefixed targets from the export set. The sfml-
prefixed targets are still available within the build tree but not to
downstream users thus making this an API breaking change when compared
to the 2.x releases. To keep things consistent, usage of the sfml-
targets were replaced with their namespaced counterparts.
This has a number of benefits:
1. It's more idiomatic. Modern CMake libraries are expected to
have namespaced targets.
2. Namespaced targets are less likely to collide with user-defined
targets. No one will accidentally define a SFML:: target.
3. If a namespaced target is not found by CMake, configuration
will immediately stop.
