Compiler extensions are disabled before the first `project` call to
force CMake into considering compilers to not support GNU extensions
(even though clang and gcc do).
Also sets common clang compiler options so they can be used across all
supported platforms.
`openmp-simd` support is enabled by default as there is no performance
penalty on x86_64 systems and intrinsics are enabled on arm64.
Also implements CMake's `CMAKE_COMPILE_WARNING_AS_ERROR` flag to
enable the desired behavior and configuration time.
Include guards ensure that bootstrap includes happen only once for the
entire project. Moving all policy changes into an included file without
its own policy scope ensures that the policy is applied to the project.
Camera Extensions require specific entitlements for the hosting app,
which also require a provisioning profile. To avoid breaking local
builds that do not require the camera extension, an additional
entitlements file that will not trigger the provisioning profile
requirement will be used if the virtualcam (but not the Camera
Extension) is configured.
- Sets CMAKE_C_STANDARD to 17
- Disables C extensions (e.g. gnu17) to force ISO C on macOS/Windows
- Fixes language properties in cmake 3.0 not being set correctly
- Sets Xcode attributes to c17
