Merge pull request #298683 from FlafyDev/flutter-gradle-fix

          "dartSdkVersion": "${dart.version}"

        }

        EOF

        # Suppress a small error now that `.gradle`'s location changed.

        # Location changed because of the patch "gradle-flutter-tools-wrapper.patch".

        mkdir -p "$out/packages/flutter_tools/gradle/.gradle"

      '';

      installPhase = ''

This patch introduces an intermediate Gradle build step to alter the behavior

of flutter_tools' Gradle project, specifically moving the creation of `build`

and `.gradle` directories from within the Nix Store to somewhere in `$HOME/.cache/flutter/nix-flutter-tools-gradle/$engineShortRev`.

Without this patch, flutter_tools' Gradle project tries to generate `build` and `.gradle`

directories within the Nix Store. Resulting in read-only errors when trying to build a

Flutter Android app at runtime.

This patch takes advantage of the fact settings.gradle takes priority over settings.gradle.kts to build the intermediate Gradle project

when a Flutter app runs `includeBuild("${settings.ext.flutterSdkPath}/packages/flutter_tools/gradle")`

`rootProject.buildFileName = "/dev/null"` so that the intermediate project doesn't use `build.gradle.kts` that's in the same directory.

The intermediate project makes a `settings.gradle` file in `$HOME/.cache/flutter/nix-flutter-tools-gradle/<short engine rev>/` and `includeBuild`s it.

This Gradle project will build the actual `packages/flutter_tools/gradle` project by setting

`rootProject.projectDir = new File("$settingsDir")` and `apply from: new File("$settingsDir/settings.gradle.kts")`.

Now the `.gradle` will be built in `$HOME/.cache/flutter/nix-flutter-tools-gradle/<short engine rev>/`, but `build` doesn't.

To move `build` to `$HOME/.cache/flutter/nix-flutter-tools-gradle/<short engine rev>/` as well, we need to set `buildDirectory`.

diff --git a/packages/flutter_tools/gradle/settings.gradle b/packages/flutter_tools/gradle/settings.gradle

new file mode 100644

index 0000000000..b2485c94b4

--- /dev/null

+++ b/packages/flutter_tools/gradle/settings.gradle

@@ -0,0 +1,19 @@

+rootProject.buildFileName = "/dev/null"

+

+def engineShortRev = (new File("$settingsDir/../../../bin/internal/engine.version")).text.take(10)

+def dir = new File("$System.env.HOME/.cache/flutter/nix-flutter-tools-gradle/$engineShortRev")

+dir.mkdirs()

+def file = new File(dir, "settings.gradle")

+

+file.text = """

+rootProject.projectDir = new File("$settingsDir")

+apply from: new File("$settingsDir/settings.gradle.kts")

+

+gradle.allprojects { project ->

+  project.beforeEvaluate {

+    project.layout.buildDirectory = new File("$dir/build")

+  }

+}

+"""

+

+includeBuild(dir)