Automatically rebuild unit testing build directory with each unit/functional testing run

[glemieux]

Describe the changes

If possible, automatically rebuild the _build directory. This could be achieved simply by rm -rf the build directory with each call to the main script.

Is your request related to a problem?

I ran into #1441 due to an out-of-date env_mach_specific.xml in the _build directory of the fates base directory.

Alternative options

It might be possible that the machine config file is the only thing not being rebuilt. Looking at the CIME code it appears that this warning is found in the configure.py module: https://github.com/ESMCI/cime/blob/61a98165c0733ce8a7793c731bfee3def9c70d01/CIME/BuildTools/configure.py#L193-L199

Per conversations with @adrifoster about #1428, we currently use the configure (and other CIME functions) to get the cmake argument list values. If we could avoid using these CIME calls, this would also avoid the issue.

fates/testing/build_fortran_tests.py

Lines 113 to 144 in 49cd7d0

	# create the environment, and the Macros.cmake file
	configure(
	machobj,
	build_dir,
	["CMake"],
	compiler,
	mpilib,
	True,
	"nuopc",
	os_,
	unit_testing=True,
	)
	machspecific = EnvMachSpecific(build_dir, unit_testing=True)
	# make a fake case
	fake_case = FakeCase(compiler, mpilib, True, "nuopc", threading=False)
	machspecific.load_env(fake_case)
	# create cmake argument list with information from the fake case and machine object
	cmake_args_list = [
	f"-DOS={os_}",
	f"-DMACH={machobj.get_machine_name()}",
	f"-DCOMPILER={compiler}",
	f"-DDEBUG={stringify_bool(True)}",
	f"-DMPILIB={mpilib}",
	f"-Dcompile_threaded={stringify_bool(False)}",
	f"-DCASEROOT={build_dir}"
	]
	cmake_args = " ".join(cmake_args_list)
	return cmake_args

Additional context

No response

[glemieux]

🤦 I just realized there is an option that we can pass to do this: --clean. Closing.