cmake with unix makefiles fails to resolve dist dependencies
added from COPY_FROM_BUILD if these dependencies aren't built yet.
This commit replaces the COPY_FROM_BUILD based logic with two new functions
'dist_add_configured' and 'dist_add_generated' to indicate which files should
be included in the dist tarball. The latter also adds a target level dependency
to the dist tarball custom command. Hence the former should
be used for files that get generated during a cmake run while the latter
should be used for files generated as the result of a 'make/ninja-build' run
(like files for which an add_custom_command rule exists).
Note: this commit also temporarily disables the dist target when building
from a tarball (and hence it won't be tested in distcheck either). This
will be handled in a future commit.
set(dist_generated_depends${local_generated_depends}CACHEINTERNAL"global targets for generated files that will be included in the distribution tarball")