Add .jerbuild config for `jerbuild build`

ober

bf8439ec61fbc7cf2582a0837f32880d0f9ebfdd

diff --git a/.jerbuild b/.jerbuild
new file mode 100644
index 0000000..6c7c4b5
--- /dev/null
+++ b/.jerbuild
@@ -0,0 +1,6 @@
+;; jerbuild build config for gitsafe.
+;; All paths are relative to this file.
+
+(entry  "gitsafe/main.ss")
+(output "gitsafe-bin")
+(libdirs ".")