Add NONE option for --with-linux and --with-spl.

This is used when you need to configure the project but you don't
actually intend to build it.  Thus you don't really need access to
either the kernel or spl headers and symbols.  At Livermore I use
this when I only intend to use the 'make dist' or 'make srpm' target.

config/zfs-build.m4

@@ -14,24 +14,21 @@ AC_DEFUN([ZFS_AC_KERNEL], [
 	AC_MSG_CHECKING([kernel source directory])
 	if test -z "$kernelsrc"; then
 		kernelbuild=
-		sourcelink=/lib/modules/${ver}/source
+		sourcelink=`ls -1d /usr/src/kernels/* /usr/src/linux-* 2>/dev/null | tail -1`
-		buildlink=/lib/modules/${ver}/build
 
 		if test -e $sourcelink; then
-			kernelsrc=`(cd $sourcelink; /bin/pwd)`
+			kernelsrc=`readlink -f ${sourcelink}`
-		fi
+			kernelbuild=${kernelsrc}
-		if test -e $buildlink; then
+		else
-			kernelbuild=`(cd $buildlink; /bin/pwd)`
-		fi
-		if test -z "$kernelsrc"; then
-			kernelsrc=$kernelbuild
-		fi
-		if test -z "$kernelsrc" -o -z "$kernelbuild"; then
 			AC_MSG_RESULT([Not found])
 			AC_MSG_ERROR([
 			*** Please specify the location of the kernel source
 			*** with the '--with-linux=PATH' option])
 		fi
+	else
+		if test "$kernelsrc" = "NONE"; then
+			kernsrcver=NONE
+		fi
 	fi
 
 	AC_MSG_RESULT([$kernelsrc])
@@ -65,7 +62,6 @@ AC_DEFUN([ZFS_AC_KERNEL], [
 
 	AC_MSG_RESULT([$kernsrcver])
 
-	kmoduledir=${INSTALL_MOD_PATH}/lib/modules/$kernsrcver
 	LINUX=${kernelsrc}
 	LINUX_OBJ=${kernelbuild}
 	LINUX_VERSION=${kernsrcver}
@@ -73,7 +69,6 @@ AC_DEFUN([ZFS_AC_KERNEL], [
 	AC_SUBST(LINUX)
 	AC_SUBST(LINUX_OBJ)
 	AC_SUBST(LINUX_VERSION)
-	AC_SUBST(kmoduledir)
 ])
 
 AC_DEFUN([ZFS_AC_SPL], [
@@ -90,7 +85,7 @@ AC_DEFUN([ZFS_AC_SPL], [
 
 
 	AC_MSG_CHECKING([spl source directory])
-	if test -z "$splsrc" -o -z "$splbuild"; then
+	if test -z "$splsrc"; then
 		sourcelink=${LINUX}/include/spl
 		buildlink=${LINUX_OBJ}/include/spl
 
@@ -109,6 +104,11 @@ AC_DEFUN([ZFS_AC_SPL], [
 			*** Please specify the location of the spl source
 			*** with the '--with-spl=PATH' option])
 		fi
+	else
+		if test "$splsrc" = "NONE"; then
+			splsymvers=NONE
+			splsrcver=NONE
+		fi			
 	fi
 
 	AC_MSG_RESULT([$splsrc])