Go back to NDK 21

This is a partial revert of 796716c
Rust's libstd is built against a lower NDK.
Newer NDKs have replaced libgcc with libunwind. This breaks the built
now (see rust-lang/rust#85806).
Additionally some tooling changed so now the rust-android-gradle plugin breaks.
For now we drop back to the old NDK until we invest time to do a proper
upgrade.

.circleci/config.yml

@@ -100,7 +100,7 @@ commands:
           command: |
               sdkmanager \
                 "build-tools;33.0.0" \
-                "ndk;25.0.8775105"
+                "ndk;21.3.6528147"
 
   android-setup:
     steps:

build.gradle

@@ -36,7 +36,7 @@ buildscript {
     ]
 
     ext.build = [
-        ndkVersion: "25.0.8775105", // Keep it in sync in TC Dockerfile.
+        ndkVersion: "21.3.6528147", // Keep it in sync in TC Dockerfile.
         compileSdkVersion: 32,
         targetSdkVersion: 32,
         minSdkVersion: 21, // So that we can publish for aarch64.

docs/dev/android/sdk-ndk-versions.md

@@ -7,8 +7,8 @@ The Glean SDK implementation is currently build against the following versions:
     * or install with: `sdkmanager --verbose "platforms;android-32"`
 * Android Command line tools
     * Download link: <https://dl.google.com/android/repository/commandlinetools-linux-8512546_latest.zip>
-* NDK r25
-    * Download link: <https://dl.google.com/android/repository/android-ndk-r25-linux-x86_64.zip>
+* NDK r21
+    * Download link: <https://dl.google.com/android/repository/android-ndk-r21-linux-x86_64.zip>
 
 For the full setup see [Setup the Android Build Environment](setup-android-build-environment.html).
 
@@ -26,4 +26,4 @@ All locations need to be updated on upgrades:
         * `ENV ANDROID_BUILD_TOOLS "33.0.0"`
         * `ENV ANDROID_SDK_VERSION "8512546"`
         * `ENV ANDROID_PLATFORM_VERSION "32"`
-        * `ENV ANDROID_NDK_VERSION "25.0.8775105"`
+        * `ENV ANDROID_NDK_VERSION "21.3.6528147"`

docs/dev/android/setup-android-build-environment.md

@@ -23,7 +23,7 @@ If Android Studio asks you to upgrade the version of Gradle, decline.
 The following dependencies can be installed in Android Studio through `Tools > SDK Manager > SDK Tools`:
 
 - Android SDK Tools (may already be selected)
-- NDK r25
+- NDK r21
 - CMake
 - LLDB
 
@@ -46,10 +46,10 @@ sdk.dir=/path/to/sdk
 For the Android NDK:
 
 1. Download NDK r21 from <https://developer.android.com/ndk/downloads>.
-2. Extract it and put it somewhere (`$HOME/.android-ndk-r25` is a reasonable choice, but it doesn't matter).
+2. Extract it and put it somewhere (`$HOME/.android-ndk-r21` is a reasonable choice, but it doesn't matter).
 3. Add the following line to the `local.properties` file in the root of the Glean checkout (create the file if it does not exist):
    ```
-   ndk.dir=/path/to/.android-ndk-r25
+   ndk.dir=/path/to/.android-ndk-r21
    ```
 
 ### Setting up Rust

taskcluster/docker/linux/Dockerfile

@@ -25,7 +25,7 @@ WORKDIR /builds/worker/
 ENV ANDROID_BUILD_TOOLS "33.0.0"
 ENV ANDROID_TOOLS_VERSION "8512546"
 ENV ANDROID_PLATFORM_VERSION "32"
-ENV ANDROID_NDK_VERSION "25.0.8775105"
+ENV ANDROID_NDK_VERSION "21.3.6528147"
 
 # Set up the language variables to avoid problems (we run locale-gen later).
 ENV LANG en_US.UTF-8