cmake: clean unreferenced functions from OpenCV modules too

cmake/OpenCVCompilerOptions.cmake

@@ -179,12 +179,24 @@ if(CV_GCC OR CV_CLANG)
       string(REPLACE "-ffunction-sections" "" ${flags} "${${flags}}")
       string(REPLACE "-fdata-sections" "" ${flags} "${${flags}}")
     endforeach()
-  elseif(NOT ((IOS OR ANDROID) AND NOT BUILD_SHARED_LIBS) AND NOT MSVC)
-    # Remove unreferenced functions: function level linking
-    add_extra_compiler_option(-ffunction-sections)
-    add_extra_compiler_option(-fdata-sections)
-    if(NOT APPLE AND NOT OPENCV_SKIP_GC_SECTIONS)
-      set(OPENCV_EXTRA_EXE_LINKER_FLAGS "${OPENCV_EXTRA_EXE_LINKER_FLAGS} -Wl,--gc-sections")
+  else()
+    if(MSVC)
+      # TODO: Clang/C2 is not supported
+    elseif(((IOS OR ANDROID) AND NOT BUILD_SHARED_LIBS) AND NOT OPENCV_FORCE_FUNCTIONS_SECTIONS)
+      # don't create separate sections for functions/data, reduce package size
+    else()
+      # Remove unreferenced functions: function level linking
+      add_extra_compiler_option(-ffunction-sections)
+      add_extra_compiler_option(-fdata-sections)
+      if(NOT OPENCV_SKIP_GC_SECTIONS)
+        if(APPLE)
+          set(OPENCV_EXTRA_EXE_LINKER_FLAGS "${OPENCV_EXTRA_EXE_LINKER_FLAGS} -Wl,-dead_strip")
+          set(OPENCV_EXTRA_SHARED_LINKER_FLAGS "${OPENCV_EXTRA_SHARED_LINKER_FLAGS} -Wl,-dead_strip")
+        else()
+          set(OPENCV_EXTRA_EXE_LINKER_FLAGS "${OPENCV_EXTRA_EXE_LINKER_FLAGS} -Wl,--gc-sections")
+          set(OPENCV_EXTRA_SHARED_LINKER_FLAGS "${OPENCV_EXTRA_SHARED_LINKER_FLAGS} -Wl,--gc-sections")
+        endif()
+      endif()
     endif()
   endif()