Touch the compile path when writing .app file for the first time

Closes #14049.

Author: josevalim

lib/mix/lib/mix/tasks/compile.app.ex

@@ -189,6 +189,13 @@ defmodule Mix.Tasks.Compile.App do
       Mix.Project.ensure_structure()
       File.write!(target, IO.chardata_to_string(contents))
       File.touch!(target, new_mtime)
+
+      # If we just created the .app file, it will have touched
+      # the directory mtime, so we need to reset it.
+      if current_properties == [] do
+        File.touch!(compile_path, new_mtime)
+      end
+
       Mix.shell().info("Generated #{app} app")
       {:ok, []}
     else

lib/mix/test/mix/tasks/compile.app_test.exs

@@ -66,8 +66,6 @@ defmodule Mix.Tasks.Compile.AppTest do
   test "generates .app file when changes happen" do
     in_fixture("no_mixfile", fn ->
       Mix.Project.push(MixTest.Case.Sample)
-      # Pre-create the compilation path to avoid mtime races
-      File.mkdir_p(Mix.Project.compile_path())
 
       Mix.Tasks.Compile.Elixir.run([])
       assert Mix.Tasks.Compile.App.run([]) == {:ok, []}
@@ -256,8 +254,6 @@ defmodule Mix.Tasks.Compile.AppTest do
   test ".app contains description and registered (as required by systools)" do
     in_fixture("no_mixfile", fn ->
       Mix.Project.push(MixTest.Case.Sample)
-      # Pre-create the compilation path to avoid mtime races
-      File.mkdir_p(Mix.Project.compile_path())
 
       Mix.Tasks.Compile.Elixir.run([])
       assert Mix.Tasks.Compile.App.run([]) == {:ok, []}