Unsupport the x64 shell (the flutter_tizen_shell target and flutter_tizen_shell.cc file). x64 unit tests are still supported but any x64-specific code (__X64_SHELL__) will be removed in the future in favor of https://github.com/flutter-tizen/engine/issues/239.
Part of https://github.com/flutter-tizen/engine/issues/239.
flutter_tizen_unitteststarget support all profiles by adding a necessary ldflag. This is now possible:flutter_tizen_shelltarget andflutter_tizen_shell.ccfile). x64 unit tests are still supported but any x64-specific code (__X64_SHELL__) will be removed in the future in favor of https://github.com/flutter-tizen/engine/issues/239.