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.
OBS CMake build framework 3.0 is a minor overhaul of version 2.0. Due
to close proximity of the 2.0 rework, the amount of actual changes to
project files are minimal and mostly concern application generation.
This commit contains the bootstrap elements only and requires
OS-specific implementations to be functional.
derrod