build: Fix errors in FreeBSD build

Fixes the following error when cross compiling:

```
--> freebsd/amd64 error: exit status 2
Stderr: # github.com/hashicorp/terraform/config/module
config/module/inode.go:18: cannot use st.Ino (type uint32) as type uint64 in return argument
```

config/module/inode.go

@@ -1,4 +1,4 @@
-// +build !windows
+// +build !windows !freebsd
 
 package module
 

config/module/inode_freebsd.go

@@ -0,0 +1,19 @@
+package module
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+)
+
+// lookup the inode of a file on posix systems
+func inode(path string) (uint64, error) {
+	stat, err := os.Stat(path)
+	if err != nil {
+		return 0, err
+	}
+	if st, ok := stat.Sys().(*syscall.Stat_t); ok {
+		return uint64(st.Ino), nil
+	}
+	return 0, fmt.Errorf("could not determine file inode")
+}