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.
This rewrites the keyword/argument parsing and handling in the
AddExternalProject module to use arguments more literally:
- The strict keyword-value pairing is gone in favor of keywords with
arbitrary non-keyword values. This avoids requiring users to escape
spaces and quotes in command lines.
- Customized step command lines are now specified with a single
keyword <step>_COMMAND instead of putting the arguments in a
separate entry (previously called <step>_ARGS).
- Build step custom commands now use VERBATIM mode so that arguments
are correctly escaped on the command line during builds.
This teaches AddExternalProject to run "$(MAKE)" for build and install
steps of CMake-based external projects when using a Makefile generator.
It allows the external project to participate in a parallel make invoked
on the superproject.
This uses the get_property command to simplify property lookup in the
AddExternalProject module. It distinguishes for build and install
argument properties the cases of unset and set to empty.
Brad King
David Cole