Support ANDROID_SDK_ROOT in addition to ANDROID_HOME (#25221)

* Fall back to ANDROID_SDK_ROOT if ANDROID_HOME is not set

And update descriptions to use the non-deprecated ANDROID_SDK_ROOT.

Fixes #15114.

* Remove trailing whitespace

* Update dev/devicelab/lib/framework/adb.dart

Co-Authored-By: DanTup <danny@tuppeny.com>

* Reformat long line

packages/flutter_tools/lib/src/android/android_sdk.dart

diff --git a/packages/flutter_tools/lib/src/android/android_sdk.dart b/packages/flutter_tools/lib/src/android/android_sdk.dart
index 2f7ffdb..7ffd46f 100644
--- a/packages/flutter_tools/lib/src/android/android_sdk.dart
+++ b/packages/flutter_tools/lib/src/android/android_sdk.dart
@@ -21,6 +21,7 @@
 AndroidSdk get androidSdk => context[AndroidSdk];
 
 const String kAndroidHome = 'ANDROID_HOME';
+const String kAndroidSdkRoot = 'ANDROID_SDK_ROOT';
 
 // Android SDK layout:
 
@@ -243,6 +244,8 @@
         androidHomeDir = config.getValue('android-sdk');
       } else if (platform.environment.containsKey(kAndroidHome)) {
         androidHomeDir = platform.environment[kAndroidHome];
+      } else if (platform.environment.containsKey(kAndroidSdkRoot)) {
+        androidHomeDir = platform.environment[kAndroidSdkRoot];
       } else if (platform.isLinux) {
         if (homeDirPath != null)
           androidHomeDir = fs.path.join(homeDirPath, 'Android', 'Sdk');

packages/flutter_tools/lib/src/android/android_workflow.dart

diff --git a/packages/flutter_tools/lib/src/android/android_workflow.dart b/packages/flutter_tools/lib/src/android/android_workflow.dart
index e1eac67..f2e7725 100644
--- a/packages/flutter_tools/lib/src/android/android_workflow.dart
+++ b/packages/flutter_tools/lib/src/android/android_workflow.dart
@@ -125,6 +125,10 @@
       final String androidHomeDir = platform.environment[kAndroidHome];
       messages.add(ValidationMessage('$kAndroidHome = $androidHomeDir'));
     }
+    if (platform.environment.containsKey(kAndroidSdkRoot)) {
+      final String androidSdkRoot = platform.environment[kAndroidSdkRoot];
+      messages.add(ValidationMessage('$kAndroidSdkRoot = $androidSdkRoot'));
+    }
 
     final List<String> validationResult = androidSdk.validateSdkWellFormed();
 

packages/flutter_tools/lib/src/android/apk.dart

diff --git a/packages/flutter_tools/lib/src/android/apk.dart b/packages/flutter_tools/lib/src/android/apk.dart
index fc28d54..41c89b0 100644
--- a/packages/flutter_tools/lib/src/android/apk.dart
+++ b/packages/flutter_tools/lib/src/android/apk.dart
@@ -30,7 +30,7 @@
 
   // Validate that we can find an android sdk.
   if (androidSdk == null)
-    throwToolExit('No Android SDK found. Try setting the ANDROID_HOME environment variable.');
+    throwToolExit('No Android SDK found. Try setting the ANDROID_SDK_ROOT environment variable.');
 
   final List<String> validationResult = androidSdk.validateSdkWellFormed();
   if (validationResult.isNotEmpty) {