refactor: use execPath where appropriate

format.ts

@@ -1,12 +1,12 @@
 #!/usr/bin/env deno --allow-run --allow-write --allow-read
 // Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
-const { exit, args } = Deno;
+const { exit, args, execPath } = Deno;
 import { parse } from "./flags/mod.ts";
-import { xrun, executableSuffix } from "./prettier/util.ts";
+import { xrun } from "./prettier/util.ts";
 
 async function main(opts) {
   const args = [
-    `deno${executableSuffix}`,
+    execPath,
     "--allow-write",
     "--allow-read",
     "prettier/main.ts",

prettier/main_test.ts

@@ -2,8 +2,8 @@
 import { join } from "../fs/path.ts";
 import { assertEquals } from "../testing/asserts.ts";
 import { test } from "../testing/mod.ts";
-import { xrun, executableSuffix } from "./util.ts";
-const { readAll } = Deno;
+import { xrun } from "./util.ts";
+const { readAll, execPath } = Deno;
 
 const decoder = new TextDecoder();
 
@@ -19,7 +19,7 @@ async function run(
 }
 
 const cmd = [
-  `deno${executableSuffix}`,
+  execPath,
   "--allow-run",
   "--allow-write",
   "--allow-read",

prettier/util.ts

@@ -8,5 +8,3 @@ export function xrun(opts): Deno.Process {
     args: build.os === "win" ? ["cmd.exe", "/c", ...opts.args] : opts.args
   });
 }
-
-export const executableSuffix = build.os === "win" ? ".exe" : "";