FIX: SWIG Bindings: Use correct SWIG executable and adapt for Apple ld

This commit introduces two changes:
    (1) It correctly sets the SWIG executable for Apple targets.
    (2) It adapts to the Apple linker (ld), which does not allow undefined symbols in shared objects (.so) by default.

Regarding (2), see SWIG issue 2469.

Signed-off-by: Philipp Remy <philipp.remy@law-school.de>

Author: philippremy

src/cmake/Dependencies.cmake

@@ -1555,10 +1555,17 @@ if(AV_BUILD_SWIG)
         DEPENDS ${PCRE2_TARGET}
     )
 
-    set(SWIG_CMAKE_FLAGS
-        -DSWIG_DIR=${CMAKE_INSTALL_PREFIX}/share/swig/4.3.0
-        -DSWIG_EXECUTABLE=${CMAKE_INSTALL_PREFIX}/bin-deps
-    )
+    if(APPLE)
+        set(SWIG_CMAKE_FLAGS
+            -DSWIG_DIR=${CMAKE_INSTALL_PREFIX}/share/swig/4.3.0
+            -DSWIG_EXECUTABLE=${CMAKE_INSTALL_PREFIX}/bin/swig
+        )
+    else()
+        set(SWIG_CMAKE_FLAGS
+            -DSWIG_DIR=${CMAKE_INSTALL_PREFIX}/share/swig/4.3.0
+            -DSWIG_EXECUTABLE=${CMAKE_INSTALL_PREFIX}/bin-deps
+        )
+    endif()
 endif()
 
 if(AV_BUILD_XERCESC)

src/cmake/Helpers.cmake

@@ -365,6 +365,15 @@ function(alicevision_swig_add_library module_name)
         TARGET ${module_name}
         PROPERTY COMPILE_OPTIONS -std=c++20
     )
+    if(APPLE)
+        # The ld on macOS does not allow undefined symbols for shared objects,
+        # so this must be explicitly passed to the linker.
+        # See: https://github.com/swig/swig/issues/2469
+        set_property(
+            TARGET ${module_name}
+            PROPERTY LINK_OPTIONS -undefined dynamic_lookup
+        )
+    endif()
 
     target_link_libraries(${module_name}
         PUBLIC ${SWIG_MODULE_PUBLIC_LINKS}