Modify CMake to make more things actually optional

[CoryMartin-NOAA]

For example:

ioda-converters/CMakeLists.txt

Lines 163 to 177 in e220318

	if( eckit_FOUND AND oops_FOUND AND ioda_FOUND )
	set(iodaconv_gsi_varbc_ENABLED True)
	message(STATUS "Enabled Component: gsi bias converter")
	else()
	set(iodaconv_gsi_varbc_ENABLED False)
	message(STATUS "Disabled Component: gsi bias converter")
	endif()
	if (NetCDF_Fortran_FOUND )
	set(iodaconv_obserror_ENABLED True)
	message(STATUS "Enabled Component: obserror converter")
	else()
	set(iodaconv_obserror_ENABLED False)
	message(STATUS "Disabled Component: obserror converter")
	endif()

These options are controlled by the presence of libraries but I don't think (according to Google Gemini LLM) we can actually overwrite these with CMake commands at the command line because they are not "options". We should have something like:

option( build_iodaconv_gsi_varbc ON)
if( eckit_FOUND AND oops_FOUND AND ioda_FOUND AND build_iodaconv_gsi_varbc )
    set(iodaconv_gsi_varbc_ENABLED True)
    message(STATUS "Enabled Component: gsi bias converter")
else()
    set(iodaconv_gsi_varbc_ENABLED False)
    message(STATUS "Disabled Component: gsi bias converter")
endif()