In Apple clang 11 (Xcode 11) experimental/optional emits a warning that it has been removed, i.e building with xcode 11 fails as it seems experimental::optional is available.
This PR fixes that by not setting MODERN_SQLITE_EXPERIMENTAL_OPTIONAL_SUPPORT if building with Apple clang 11 or above.
In Apple clang 11 (Xcode 11) experimental/optional emits a warning that it has been removed, i.e building with xcode 11 fails as it seems experimental::optional is available. This PR fixes that by not setting MODERN_SQLITE_EXPERIMENTAL_OPTIONAL_SUPPORT if building with Apple clang 11 or above.