Preserve --compile-no-warning-as-error in automatic CMake re-runs

When the build system re-runs `cmake` to regenerate itself, preserve the
`--compile-no-warning-as-error` option if it was used when `cmake` was
last explicitly invoked.  Normally such settings are preserved in the
cache, but the purpose of this option is to be beyond the reach of
project code.
7 files changed