Do not require generated API manuals when POD documentation is disabled.

--- docs/Makefile.am.orig	2025-11-18 10:43:55 UTC
+++ docs/Makefile.am
@@ -27,7 +27,9 @@ sinclude $(srcdir)/Makefile.inc
 # prior to its 'all-am: Makefile $(MANS)' rule, which gets parsed before
 # $(MANS) has grown in size, so we have to add a second all-am dependency.
 sinclude $(srcdir)/Makefile.inc
+if HAVE_POD
 all-am: $(api_built:%=%.3)
+endif HAVE_POD
 
 generator_built = \
 	Makefile.inc \