In the `try_compile` source file signature we propagate the caller's
value of `CMAKE_<LANG>_FLAGS` into the test project. Extend this to
propagate `CMAKE_<LANG>_FLAGS_<CONFIG>` too instead of always using the
default value in the test project. This will be useful, for example, to
allow the MSVC runtime library to be changed (e.g. `-MDd` => `-MTd`).
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.
With the Makefile and Ninja generators we expect that touching the input
source file for a try_compile will cause CMake to re-run on the next
build. Extend the RunCMake.try_compile test with a case covering this.
Also check that CMake does not re-run if nothing has changed.
Copy CMAKE_EXE_LINKER_FLAGS into the test project generated by
try_compile, just like we already copy CMAKE_<LANG>_FLAGS.
Add CMake Policy CMP0056 to activate this behavior in a compatible way,
but do not warn by default when the policy is not set since it will
affect all try_compile calls.
Extend the RunCMake.try_compile test with a case covering this behavior
for each policy setting.
When the COPY_FILE operation fails optionally capture the error message
with a COPY_FILE_ERROR option instead of reporting the error
immediately. This gives callers a chance to do something else or report
the error.
Teach the RunCMake.try_compile test to cover bad argument combinations
involving COPY_FILE_ERROR. Teach the TryCompile test to cover the case
of a COPY_FILE error message captured by COPY_FILE_ERROR.
Extend the signature
try_compile(RESULT_VAR <bindir> <srcfile> ...)
to allow multiple sources as
try_compile(RESULT_VAR <bindir> SOURCES <srcfile>... ...)
Process the sources to generate a CMakeLists.txt that enables all needed
languages.
Teach the TryCompile test to try cases with two sources of the same
language and of mixed languages. Teach RunCMake.try_compile to cover
error cases for the signature.
Process all arguments in a single loop using a simple state machine.
While at it, fix some error message typos. Also allow LINK_LIBRARIES
with no actual libraries to disable use of the -DLINK_LIBRARIES=...
from the CMAKE_FLAGS. This was already possible in the old logic if
LINK_LIBRARIES was immediately followed by another keyword argument
instead of the end of the argument list, so allow it in general.
Update the RunCMake.try_compile test cases accordingly.
Brad King