Support out-of-tree testing with CMake

Create extra symbolic links with CMake so that SSL testing (ssl-opt.sh
and compat.sh) works in out-of-tree builds.

tests/CMakeLists.txt

@@ -105,26 +105,11 @@ add_test_suite(xtea)
 add_test_suite(x509parse)
 add_test_suite(x509write)
 
-# Make data_files available in an out-of-source build
+# Make scripts and data files needed for testing available in an
+# out-of-source build.
 if (NOT ${CMAKE_CURRENT_BINARY_DIR} STREQUAL ${CMAKE_CURRENT_SOURCE_DIR})
-    # Get OS dependent path to use in `execute_process`
-    file(TO_NATIVE_PATH "${CMAKE_CURRENT_BINARY_DIR}/data_files" link)
-    file(TO_NATIVE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/data_files" target)
-
-    if (NOT EXISTS ${link})
-        if (CMAKE_HOST_UNIX)
-            set(command ln -s ${target} ${link})
-        else()
-            set(command cmd.exe /c mklink /j ${link} ${target})
-        endif()
-
-        execute_process(COMMAND ${command}
-                        RESULT_VARIABLE result
-                        ERROR_VARIABLE output)
-
-        if (NOT ${result} EQUAL 0)
-            message(FATAL_ERROR "Could not create symbolic link for: ${target} --> ${output}")
-        endif()
-    endif()
+    link_to_source(compat.sh)
+    link_to_source(data_files)
+    link_to_source(scripts)
+    link_to_source(ssl-opt.sh)
 endif()
-