Refactor CMake compiler options

Refactor CMake compiler options

Create the target loader_common_options which will contain the compiler
commands, options, and definitions that is shared across the code base.
This includes linking to platform_wsi_defines and moving many of the defines
found in the loader/CMakelists.txt up to this location.

Setting the language standard through an interface target is not possible, so
to avoid using the global state modifiers, each target needing to be on a
specific language standard must specify it for themselves.

Note that this commit is in a series and is not intended to work by itself.