[source] build: set TMPDIR for opkg calls

[LEDE Commits]

nbd pushed a commit to source.git, branch master:
https://git.lede-project.org/?p=source.git;a=commitdiff;h=653cb2594d34439f292cf973747ee84bb266ca9e

commit 653cb2594d34439f292cf973747ee84bb266ca9e
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Fri Jul 22 13:04:11 2016 +0200

    build: set TMPDIR for opkg calls
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 include/rootfs.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/rootfs.mk b/include/rootfs.mk
index 2143ef8..f3ba33a 100644
--- a/include/rootfs.mk
+++ b/include/rootfs.mk
@@ -37,6 +37,7 @@ endif
 opkg = \
   IPKG_NO_SCRIPT=1 \
   IPKG_INSTROOT=$(1) \
+  TMPDIR=$(1)/tmp \
   $(STAGING_DIR_HOST)/bin/opkg \
 	--offline-root $(1) \
 	--force-depends \