Ability to flag features/plugins support by Operating System

[edsiper]

As Fluent Bit is becoming portable between Linux, OSX and BSD, it should expose some mechanism to whitelist the features allowed for the target system (some plugins may not work on all systems)

[edsiper]

There is a workaround that have been there for a while:

https://github.com/fluent/fluent-bit/blob/master/plugins/CMakeLists.txt#L66