build: set cmake min version to 3.0 to fix deprecation warning

build: set cmake min version to 3.0 to fix deprecation warning

| Compatibility with CMake < 2.8.12 will be removed from a future version of
| CMake.
|
| Update the VERSION argument <min> value or use a ...<max> suffix to tell
| CMake that the project does not need compatibility with older versions.

Signed-off-by: Christian Lamparter <chunkeey@gmail.com>