Get "make install" to install DSOs again.

static has just the list of static modules for this directory, so
in all but one of our module directories mod_so won't be in this
list, preventing us from thinking this is a DSO build.

BUILTIN_LIBS is always a valid check since it is the entire list
of modules.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87299 13f79535-47bb-0310-9956-ffa450edef68