Tests: Rename OS X nightly release binary test

The "Mac64" build is now the primary and only OS X build, so just name
it "OSX".

Tests/CMakeLists.txt

@@ -687,7 +687,7 @@ ${CMake_BINARY_DIR}/bin/cmake -DDIR=dev -P ${CMake_SOURCE_DIR}/Utilities/Release
   if(CMAKE_BUILD_NIGHTLY_RELEASES)
     ADD_NIGHTLY_BUILD_TEST(CMakeNightlyWindows
       dash2win64_release.cmake)
-    ADD_NIGHTLY_BUILD_TEST(CMakeNightlyMac64
+    ADD_NIGHTLY_BUILD_TEST(CMakeNightlyOSX
       dashmacmini5_release.cmake)
     ADD_NIGHTLY_BUILD_TEST(CMakeNightlyLinux
       magrathea_release.cmake)