Add macOS support

[jcfr]

Summary

On macOS, build Autoscoper with:

• Build Autoscoper as a regular executable on macOS so that it is build and packaged in a "standard" location without the autoscoper.app folder.

• On macOS, set Autoscoper_INSTALL_DEPENDENCIES set to OFF. Associated dependencies are copied into the package leveraging the fix-up process.

• Add Autoscoper external project step to change back @rpath references into the corresponding build-tree absolute paths. This ensures that the fix-up process can lookup each library and executable dependencies.

• Ensure the autoscoper executable can resolve its dependency setting Autoscoper_EXECUTABLE_LINK_FLAGS to ${Slicer_INSTALL_THIRDPARTY_EXECUTABLE_LINK_FLAGS}.

  • For reference, Slicer_INSTALL_THIRDPARTY_EXECUTABLE_LINK_FLAGS is itself set to a value similar to -Wl,-rpath,@loader_path/relative/path/"

.. and also increases the wait time before attempting to connect to the autoscoper process.

List of Autoscoper changes

$ git shortlog b29d30f51..48286c33c --no-merges
Jean-Christophe Fillion-Robin (4):
      COMP: Add support for building Autoscoper as a regular executable on macOS
      COMP: Ensure Autoscoper_*_DIR variables are passed to inner build
      COMP: Fix support for building on macOS
      COMP: Fix Slicer extension packaging allowing customizing autoscoper link flags

[jcfr]

Inspecting the dependencies associated with the packaged libtiff, the zstd dependencies should be explicitly disabled.

$ otool -L _CPack_Packages/Darwin/TGZ/31807-macosx-amd64-SlicerAutoscoperM-git0172c84-2023-06-23/Slicer.app/Contents/Extensions-31807/SlicerAutoscoperM/lib/Slicer-5.3/libtiff.5.8.0.dylib 
_CPack_Packages/Darwin/TGZ/31807-macosx-amd64-SlicerAutoscoperM-git0172c84-2023-06-23/Slicer.app/Contents/Extensions-31807/SlicerAutoscoperM/lib/Slicer-5.3/libtiff.5.8.0.dylib:
    @rpath/Extensions-31807/SlicerAutoscoperM/lib/Slicer-5.3/libtiff.5.8.0.dylib (compatibility version 5.0.0, current version 5.8.0)
    /usr/lib/libz.1.dylib (compatibility version 1.0.0, current version 1.2.11)
    /usr/local/opt/zstd/lib/libzstd.1.dylib (compatibility version 1.0.0, current version 1.5.2)
    /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1319.100.3)

[jcfr]

Local testing confirmed the extension can be built and packages on Linux, macOS and Windows :heavy_check_mark: