Clarify that MAKEOBJDIRPREFIX and MAKEOBJDIR are not

honored as make(1) arguments.

Requested by:	smh
MFC After:	3 days
Sponsored by:	The FreeBSD Foundation

share/man/man5/make.conf.5

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 28, 2013
+.Dd May 2, 2014
 .Dt MAKE.CONF 5
 .Os
 .Sh NAME
@@ -692,6 +692,8 @@ and
 .Ev MAKEOBJDIR
 are environment variables and should not be set in
 .Nm
+or as command line arguments to
+.Xr make 1 ,
 but in make's environment.
 .Sh BUGS
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