Update target linking

Author: alexbeattie42

cmake/OpenSimMacros.cmake

@@ -386,20 +386,27 @@ function(OpenSimAddTests)
             set_target_properties(${TEST_NAME} PROPERTIES
                 FOLDER "Tests"
             )
+            # Link data files to build directory.
+            foreach(data_file ${OSIMADDTESTS_DATAFILES})
+                # This command symlinks the data files
+                # from the source directories into the running directory.
+                # This preserves changes to source files.
+                get_filename_component(FILENAME ${data_file} NAME)
+                set(link_path "${CMAKE_CURRENT_BINARY_DIR}/${FILENAME}")
+                if(NOT EXISTS "${link_path}")
+                    add_custom_command(
+                        TARGET ${TEST_NAME} POST_BUILD
+                        COMMAND ${CMAKE_COMMAND} -E create_symlink
+                            "${data_file}"
+                            "${link_path}"
+                        COMMENT "Creating symlink: ${data_file} -> ${link_path}"
+                    )
+                else()
+                    message(STATUS "Skipping ${data_file}, it already exists in the build directory.")
+                endif()
+            endforeach()
         endforeach()
 
-        # Copy data files to build directory.
-        foreach(data_file ${OSIMADDTESTS_DATAFILES})
-            # This command symlinks the data files
-            # from the source directories into the running directory.
-            # This preserves changes to source files.
-            get_filename_component(FILENAME ${data_file} NAME)
-            add_custom_command(
-                TARGET ${TEST_NAME} POST_BUILD
-                COMMAND ${CMAKE_COMMAND} -E create_symlink
-                    ${data_file} 
-                    $<TARGET_FILE_DIR:${TEST_NAME}>/${FILENAME})
-        endforeach()
 
         #if(UNIX)
         #  add_definitions(-fprofile-arcs -ftest-coverage)