Add build/srcroot.go, a helper to interrogate module location.

Author: dot-asm

build/srcroot.go

@@ -0,0 +1,14 @@
+package blst
+
+import (
+    "path/filepath"
+    "runtime"
+)
+
+var SrcRoot string
+
+func init() {
+    if _, self, _, ok := runtime.Caller(0); ok {
+        SrcRoot = filepath.Dir(filepath.Dir(self))
+    }
+}