upip: bootstrap_upip.sh: Perform processing in /tmp.

upip/bootstrap_upip.sh

@@ -1,6 +1,12 @@
 # This script performs bootstrap installation of upip package manager from PyPI
 # All the other packages can be installed using it.
 
+if [ -z "$TMPDIR" ]; then
+    cd /tmp
+else
+    cd $TMPDIR
+fi
+
 # Remove any stale old version
 rm -rf micropython-upip-*
 wget -nd -r -l1 https://pypi.python.org/pypi/micropython-upip/ --accept-regex ".*pypi.python.org/packages/source/.*.gz" --reject=html