[source] base-files: upgrade: correctly handle nand_do_upgrade argument passed from preupgrade

[LEDE Commits]

neoraider pushed a commit to source.git, branch master:
https://git.lede-project.org/7a29e44f9075b14ca959a730faa7fc6e2e23393f

commit 7a29e44f9075b14ca959a730faa7fc6e2e23393f
Author: Matthias Schiffer <mschiffer at universe-factory.net>
AuthorDate: Mon Jul 10 10:35:19 2017 +0200

    base-files: upgrade: correctly handle nand_do_upgrade argument passed from preupgrade
    
    Fixes: 30f61a34b4cf "base-files: always use staged sysupgrade"
    Signed-off-by: Matthias Schiffer <mschiffer at universe-factory.net>
---
 package/base-files/files/lib/upgrade/common.sh | 2 +-
 package/base-files/files/lib/upgrade/nand.sh   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/package/base-files/files/lib/upgrade/common.sh b/package/base-files/files/lib/upgrade/common.sh
index fc59bf2..c8b7101 100644
--- a/package/base-files/files/lib/upgrade/common.sh
+++ b/package/base-files/files/lib/upgrade/common.sh
@@ -211,7 +211,7 @@ default_do_upgrade() {
 do_upgrade_stage2() {
 	v "Performing system upgrade..."
 	if [ -n "$do_upgrade" ]; then
-		$do_upgrade "$IMAGE"
+		eval "$do_upgrade"
 	elif type 'platform_do_upgrade' >/dev/null 2>/dev/null; then
 		platform_do_upgrade "$IMAGE"
 	else
diff --git a/package/base-files/files/lib/upgrade/nand.sh b/package/base-files/files/lib/upgrade/nand.sh
index 6b2bdba..563db4c 100644
--- a/package/base-files/files/lib/upgrade/nand.sh
+++ b/package/base-files/files/lib/upgrade/nand.sh
@@ -289,7 +289,7 @@ nand_do_upgrade() {
 		# hook; this piece of code handles scripts that haven't been
 		# updated. All scripts should gradually move to call nand_do_upgrade
 		# from platform_do_upgrade instead.
-		export do_upgrade=nand_do_upgrade
+		export do_upgrade="nand_do_upgrade '$1'"
 		return
 	fi