The add_external_project function separates its arguments with ';'
separators, so previously no command line argument could contain one.
When specifying CMAKE_ARGS, some -D argument values may need to contain
a semicolon to form lists in the external project cache.
This adds add_external_project argument LIST_SEPARATOR to specify a list
separator string. The separator is replaced by ';' in arguments to any
command created to drive the external project. For example:
add_external_project(...
LIST_SEPARATOR ::
CMAKE_ARGS -DSOME_LIST:STRING=A::B::C
...)
passes "-DSOME_LIST:STRING=A;B;C" to CMake for the external project.
The patch step runs parallel to the update step since it does not make
sense to have both. Configuration of the step requires specification of
a PATCH_COMMAND argument to add_external_project.
Brad King