Add a `CMAKE_TRY_COMPILE_PLATFORM_VARIABLES` variable to specify a list
of custom variables to be forwarded to a `try_compile` test project.
This will be useful for platform information modules or toolchain files
to forward some platform-specific set of variables from the host project
(perhaps set in its cache) to the test project so that it can build the
same way.
Create a `CMAKE_TRY_COMPILE_TARGET_TYPE` option to specify use
of `add_library(... STATIC ...)` for the generated test project.
This will be useful for cross-compiling toolchains that cannot
link a binary without custom flags or scripts.
Set policy CMP0065 to the value used in the calling project.
Set the the value of CMAKE_ENABLE_EXPORTS if set in the calling
project to initialize the target property appropriately.
Explain that try_compile calls need to be protected with conditions to
avoid running more than once so that it is easy to isolate a single
try_compile to perform with --debug-trycompile.
Brad King
Chuck Atkins
Alan W. Irwin
Kitware Robot