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.
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.