Update Jerboa toolchain to v0.2.8

ober

12ecd6389bd4fcc178b484d3b9527fe717670ccb

diff --git a/Makefile b/Makefile
index 5804cac..89f9c2e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-JERBOA_VERSION ?= v0.2.3
+JERBOA_VERSION ?= v0.2.8
 JERBOA_TOOL_DIR ?= $(CURDIR)/.jerboa/bin
 JERBUILD ?= $(shell if [ -x "$(CURDIR)/../jerboa/dist/jerbuild" ]; then printf '%s\n' "$(CURDIR)/../jerboa/dist/jerbuild"; elif command -v jerbuild >/dev/null 2>&1; then command -v jerbuild; else printf '%s\n' "$(JERBOA_TOOL_DIR)/jerbuild"; fi)
 JH = $(shell "$(JERBUILD)" --jerboa-home 2>/dev/null)