LU-1981 build: External OSD support in configure

With configure option "--with-osd=<dir>" one can get additional
(external to main tree) directory to be built with main tree.

Change-Id: Ibe1c1d136d9c8bf8245344791f0f51933266018a
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Signed-off-by: Li Wei <liwei@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/4099


Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>

build/autoconf/lustre-build.m4

@@ -762,6 +762,7 @@ LB_PROG_CC
 
 LB_UOSS
 LB_POSIX_OSD
+LC_OSD_ADDON
 
 LB_CONFIG_DOCS
 LB_CONFIG_UTILS

lustre/Makefile.in

@@ -11,5 +11,6 @@ subdir-m += mgc
 @SERVER_TRUE@subdir-m += quota osp lod
 @CLIENT_TRUE@subdir-m += mdc lmv llite fld
 @ZFS_ENABLED_TRUE@subdir-m += osd-zfs
+@OSDADDON@
 
 @INCLUDE_RULES@

lustre/autoconf/lustre-core.m4

@@ -2273,6 +2273,46 @@ LB_LINUX_TRY_COMPILE([
 ])
 ])
 
+#
+# LC_OSD_ADDON
+#
+# configure support for optional OSD implementation
+#
+AC_DEFUN([LC_OSD_ADDON],
+[AC_MSG_CHECKING([for osd])
+AC_ARG_WITH([osd],
+	AC_HELP_STRING([--with-osd=path],
+                       [set path to optional osd]),
+        [
+		case $with_osd in
+			no)     ENABLEOSDADDON=0
+				;;
+			*)	OSDADDON="${with_osd}"
+				ENABLEOSDADDON=1
+				;;
+		esac
+	], [
+		ENABLEOSDADDON=0
+	])
+if test $ENABLEOSDADDON -eq 0; then
+	AC_MSG_RESULT([no])
+	OSDADDON=
+else
+	OSDMODNAME=`basename $OSDADDON`
+	if test -e $LUSTRE/$OSDMODNAME; then
+		AC_MSG_RESULT([can't link])
+		OSDADDON=
+	elif ln -s $OSDADDON $LUSTRE/$OSDMODNAME; then
+		AC_MSG_RESULT([$OSDMODNAME])
+		OSDADDON="subdir-m += $OSDMODNAME"
+	else
+		AC_MSG_RESULT([can't link])
+		OSDADDON=
+	fi
+fi
+AC_SUBST(OSDADDON)
+])
+
 #
 # LC_CONFIGURE
 #