Trim end and add empty line for POSIX

cli/src/format.rs

@@ -180,6 +180,9 @@ fn fmt_all<'a>(arena: &'a Bump, buf: &mut Buf<'a>, ast: &'a Ast) {
     for def in &ast.defs {
         fmt_def(buf, arena.alloc(def.value), 0);
     }
+
+    buf.trim_end();
+    buf.newline();
 }
 
 /// RemoveSpaces normalizes the ast to something that we _expect_ to be invariant under formatting.

compiler/fmt/src/lib.rs

@@ -90,4 +90,10 @@ impl<'a> Buf<'a> {
             self.spaces_to_flush = 0;
         }
     }
+
+    pub fn trim_end(&mut self) {
+        while self.text.ends_with(char::is_whitespace) {
+            self.text.truncate(self.text.len() - 1);
+        }
+    }
 }