Add arm64 Linux host support (#29)

Fixed https://github.com/sony/flutter-elinux/issues/2

lib/commands/build.dart

@@ -67,7 +67,12 @@ class BuildPackageCommand extends BuildSubCommand with ELinuxExtension {
   @override
   Future<Set<DevelopmentArtifact>> get requiredArtifacts async =>
       <DevelopmentArtifact>{
-        DevelopmentArtifact.androidGenSnapshot,
+        // Use gensnapshot for Arm64 Linux when the host is arm64 because
+        // the artifacts for arm64 host don't support self-building now.
+        if (_getCurrentHostPlatformArchName() == 'arm64')
+          DevelopmentArtifact.linux,
+        if (_getCurrentHostPlatformArchName() == 'x64')
+          DevelopmentArtifact.androidGenSnapshot,
         ELinuxDevelopmentArtifact.elinux,
       };
 

lib/commands/run.dart

@@ -5,6 +5,8 @@
 
 // @dart = 2.8
 
+import 'package:flutter_tools/src/base/os.dart';
+import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/commands/run.dart';
 
@@ -18,7 +20,17 @@ class ELinuxRunCommand extends RunCommand with ELinuxExtension {
   @override
   Future<Set<DevelopmentArtifact>> get requiredArtifacts async =>
       <DevelopmentArtifact>{
-        DevelopmentArtifact.androidGenSnapshot,
+        // Use gensnapshot for Arm64 Linux when the host is arm64 because
+        // the artifacts for arm64 host don't support self-building now.
+        if (_getCurrentHostPlatformArchName() == 'arm64')
+          DevelopmentArtifact.linux,
+        if (_getCurrentHostPlatformArchName() == 'x64')
+          DevelopmentArtifact.androidGenSnapshot,
         ELinuxDevelopmentArtifact.elinux,
       };
+
+  String _getCurrentHostPlatformArchName() {
+    final HostPlatform hostPlatform = getCurrentHostPlatform();
+    return getNameForHostPlatformArch(hostPlatform);
+  }
 }

lib/elinux_builder.dart

@@ -12,6 +12,7 @@ import 'package:flutter_tools/src/android/gradle.dart';
 import 'package:flutter_tools/src/base/analyze_size.dart';
 import 'package:flutter_tools/src/base/common.dart';
 import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/base/os.dart';
 import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/build_system/build_system.dart';
 import 'package:flutter_tools/src/cache.dart';
@@ -145,10 +146,26 @@ class ELinuxBuilder {
 
 /// See: [getTargetPlatformForName] in `build_info.dart`
 TargetPlatform _getTargetPlatformForArch(String arch) {
+  final String hostArch = _getCurrentHostPlatformArchName();
   switch (arch) {
     case 'arm64':
+      // Use gensnapshot for Arm64 Linux when the host is arm64 because
+      // the artifacts for arm64 host don't support self-building now.
+      if (hostArch == 'arm64') {
+        return TargetPlatform.linux_arm64;
+      }
       return TargetPlatform.android_arm64;
     default:
+      // Use gensnapshot for Arm64 Linux when the host is arm64 because
+      // the artifacts for arm64 host don't support self-building now.
+      if (hostArch == 'arm64') {
+        return TargetPlatform.linux_x64;
+      }
       return TargetPlatform.android_x64;
   }
 }
+
+String _getCurrentHostPlatformArchName() {
+  final HostPlatform hostPlatform = getCurrentHostPlatform();
+  return getNameForHostPlatformArch(hostPlatform);
+}