Always use /bin/sh, not the user's login shell.

Author: dag-erling

tests/shtest

@@ -14,6 +14,9 @@ JQ="$JQ -b"
 
 PATH=$JQBASEDIR:$PATH $JQBASEDIR/tests/jq-f-test.sh > /dev/null
 
+SHELL=/bin/sh
+export SHELL
+
 if [ -f "$JQBASEDIR/.libs/libinject_errors.so" ]; then
   # Do some simple error injection tests to check that we're handling
   # I/O errors correctly.