Rename `CI_HOST_ARCH` and `CI_HOST_SYSTEM`, to `CI_BUILD_ARCH` and
`CI_BUILD_SYSTEM`, following the nomenclature used by GNU Autotools.
Unfortunately, the word "host" has confusingly opposite meanings in
CMake (and Bazel, etc.) vs. Autotools (and Meson, etc.)
Remove `CI_TARGET_TRIPLET` and `CI_TARGET_ABI` (for now).
Introduce the function `ci_expr` as a fast and easy equivalent of
`expr >/dev/null`.
Rephrase the assertions using an implementation pattern that is more
expressive, yet (arguably) just as readable. Remove `ci_assert`.
Modify the main functions to display more useful information in case
of usage error.
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.
Fix ci_verify_cmake.sh: sync up CI_BUILD_TO_INSTALL_RELDIR with
CI_INSTALL_DIR. (Oopsie!)
Replace slashes, backslashes and dots with underlines in system
names and machine hardware names. These names are now included in
the output directory naming scheme.
Replace CI_SYSTEM_NAME and CI_MACHINE_NAME with CI_HOST_SYSTEM and
CI_HOST_MACHINE, respectively.
Introduce CI_TARGET_SYSTEM and CI_TARGET_MACHINE, defaulting to
CI_HOST_SYSTEM and CI_HOST_MACHINE, respectively.
Use CI_TARGET_SYSTEM and CI_TARGET_MACHINE in the naming scheme of
target build and install directories, in order to allow concurrent
verification builds for multiple cross-platform targets.
Move the common declarations and initializations from ci_verify_*.sh
to ci.lib.sh, and update them as follows:
* Simplify the ci_ function names.
* Refactor the CI_ variable names:
- Add the new variable CI_TOPLEVEL_DIR.
- Rename the variables CI_SCRIPTNAME, CI_SCRIPTDIR, etc.,
to CI_SCRIPT_NAME, CI_SCRIPT_DIR, etc.
- Rename the variables CI_SRCDIR_FROM_BUILDDIR, etc., to
CI_BUILD_TO_SRC_RELDIR, etc.
* Add new functions inside ci.lib.sh:
- Replace ci_err with ci_err_usage, ci_err_fatal, ci_err_internal.
- Add the new functions ci_warn and ci_assert.
* Simplify the ci_ function names inside ci_verify_*.sh.
