build-sys: Add --disable-manpages option
1) Embedded systems often don't want man pages on the
target; rather than pointlessly building them, then ignoring
the result, allow just not building them at all
2) When bootstrapping an operating systems, documentation is the
source of many cyclical dependencies, and allowing it to
be explicitly disabled is useful for earlier build passes.
diff --git a/Makefile.am b/Makefile.am
index 26f32cd..bc95922 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,4 +1,8 @@
-SUBDIRS = . libkmod/docs man
+SUBDIRS = . libkmod/docs
+
+if BUILD_MANPAGES
+SUBDIRS += man
+endif
DISTCLEAN_LOCAL_HOOKS =
EXTRA_DIST =