Use SF Symbols on macOS 11+
Use NSSegmentedControl instead of custom view.
Add NSImage extension to fallback loading from
assets on macOS 10.15 and older.
Also should fix sizing issues when changing pane from Options
to Files.
Fixes#2247
The problem could occur with Makefiles also.
Use `-r` option on `rm` as `*.iconset` is a directory.
Co-authored-by: Charles Kerr <charles@charleskerr.com>
For some reason, Mac client is the only project that references
libtransmission files as if they were a part of its own project, and
inconsistently so. Make the include/import style uniform an in line with
other projects.
Adjust Mac client include directory settings a bit along the way.
