ci: Improve the support for cross-build verifications
Introduce CI_TARGET_TRIPLET and CI_TARGET_ABI.
Rename CI_HOST_MACHINE and CI_TARGET_MACHINE, respectively, to
CI_HOST_ARCH and CI_TARGET_ARCH, following on the conventional
target triplet nomenclature.
Introduce CI_BUILD_SYSTEM and CI_BUILD_ARCH, following on the
GNU Autotools (host/build/target) practice and nomenclature.
Ensure that CI_TARGET_SYSTEM, CI_TARGET_ARCH and CI_TARGET_ABI
are all initialized when verifying a cross-platform build.
Work around an obscure CMake error by ensuring that CMake variables
(CMAKE_AR and CMAKE_RANLIB) are initialized to the full executable
paths of their CI_* equivalents (CI_AR and CI_RANLIB).
Implement other general-purpose improvements:
* Check all CI_NO_* variables in an arithmetic context, to allow
setting them explicitly to zero in external configurations.
* Label the assertions with descriptions of what's being asserted.
* Add more comments and tracing printouts.
4 files changed
