CMake portability improvements

[jschueller]

No description provided.

[jschueller]

@mnwright it should build now, could you restart the CI ?

[jschueller]

hello @mnwright could you look at this one please ?

[mnwright]

Could you explain the changes a little bit? My cmake is a little rusty.

[jschueller]

yes, of course:

• We must check if the -Wall flag is supported by the compiler, eg unsupported on msvc
• We build ranger as a library can be used from another c++ project
• The minimum cmake version must be incremented to 3.5 to avoid warnings (3.5 is pretty old anyways)
• We add an install rule (to be able to do "make install") so that ranger is easier to use in package managers
• We add a getopt function for targets where its unsupported (msvc)