Memory leaks when calling C.CString

[bduffany]

I found a memory leak in https://github.com/buildbuddy-io/buildbuddy/pull/2686/files in the way we were calling C.clonefile, and was curious if anybody else on GitHub was using the same problematic code pattern.

While searching across code on GitHub I found that this package has a few instances where C.CString is called, but C.free is not called on the result, which causes a memory leak for long-running applications:

• https://cs.github.com/go-darwin/apfs/blob/f84b94dbf34818a1ecdc0836be075cf386a53198/clone.go#L54
• https://cs.github.com/go-darwin/apfs/blob/f84b94dbf34818a1ecdc0836be075cf386a53198/clone.go#L82
• https://cs.github.com/go-darwin/apfs/blob/f84b94dbf34818a1ecdc0836be075cf386a53198/clone.go#L101

Not sure if this package is still maintained but figured I'd report it.