State explicitly that the PRE_LINK mode is not for targets created by
the add_custom_target command. The existing wording for PRE_BUILD being
treated as PRE_LINK by non-VS generators will now imply this restriction
for PRE_BUILD too.
Format the reStructuredText markup manually. Organize the command
options into a definition list. Use inline markup to cross-reference
related documents.
Rely on evaluation in cmCustomCommandGenerator for the generators.
When tracing target dependencies, depend on the union of dependencies
for all configurations.
Generator expressions are supported in many places and are a distinct
concept worthy of their own manual page. The old builtin documentation
was previously represented by preprocessor macros to generate it into
each place that supports them. Factor out the duplicate content into a
dedicated cmake-generator-expressions manual page and reference it from
each original location.