Add a makefile to the top level for convenience
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..43210a9
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,5 @@
+rebuild-headers:
+	mkdir -p tools/buildHeaders/build
+	cd tools/buildHeaders/build && cmake .. && cmake --build .
+	cd include/spirv/unified1 && \
+		../../../tools/buildHeaders/build/BuildSpvHeaders -H spirv.core.grammar.json