Point out that /usr/src, /usr/doc, and /usr/ports may be empty or not

exist until populated with csup(1) or svn(1).

PR:		169487
Submitted by:	Moritz Wilhelmy
MFC after:	1 day

share/man/man7/build.7

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 29, 2011
+.Dd June 27, 2012
 .Dt BUILD 7
 .Os
 .Sh NAME
@@ -39,6 +39,10 @@ normally
 .Pa /usr/doc ,
 and
 .Pa /usr/ports .
+These directories may be initially empty or non-existent until updated with
+.Xr csup 1
+or
+.Xr svn 1 .
 Directory
 .Pa /usr/src
 contains the
@@ -489,7 +493,7 @@ on built objects.
 .It Va NO_SHARE
 If set, the build does not descend into the
 .Pa /usr/src/share
-subdirectory (i.e. manpages, locale data files, timezone data files and
+subdirectory (i.e., manpages, locale data files, timezone data files and
 other
 .Pa /usr/src/share
 files will not be rebuild from their sources).
@@ -594,8 +598,10 @@ make TARGET=sparc64 DESTDIR=/clients/sparc64 installworld
 .Ed
 .Sh SEE ALSO
 .Xr cc 1 ,
+.Xr csup 1 ,
 .Xr install 1 ,
 .Xr make 1 ,
+.Xr svn 1 ,
 .Xr make.conf 5 ,
 .Xr src.conf 5 ,
 .Xr ports 7 ,