Android: add some build platform support

Author: finagolfin

Sources/Build/BuildPlan.swift

@@ -226,6 +226,8 @@ public struct BuildParameters: Encodable {
     var currentPlatform: PackageModel.Platform {
         if self.triple.isDarwin() {
             return .macOS
+        } else if self.triple.isAndroid() {
+            return .android
         } else {
             return .linux
         }

Sources/Build/Triple.swift

@@ -101,6 +101,10 @@ public struct Triple: Encodable {
         return nil
     }
 
+    public func isAndroid() -> Bool {
+        return os == .linux && abi == .android
+    }
+
     public func isDarwin() -> Bool {
         return vendor == .apple || os == .macOS || os == .darwin
     }

Sources/PackageDescription4/SupportedPlatforms.swift

@@ -37,6 +37,10 @@ public struct Platform: Encodable {
     /// The Windows platform
     @available(_PackageDescription, introduced: 5.2)
     public static let windows: Platform = Platform(name: "windows")
+
+    /// The Android platform
+    @available(_PackageDescription, introduced: 5.2)
+    public static let android: Platform = Platform(name: "android")
 }
 
 /// A platform that the Swift package supports.

Sources/PackageModel/Platform.swift

@@ -29,7 +29,7 @@ public final class PlatformRegistry {
 
     /// The static list of known platforms.
     private static var _knownPlatforms: [Platform] {
-        return [.macOS, .iOS, .tvOS, .watchOS, .linux]
+        return [.macOS, .iOS, .tvOS, .watchOS, .linux, .android]
     }
 }
 
@@ -55,6 +55,7 @@ public struct Platform: Equatable, Hashable {
     public static let tvOS: Platform = Platform(name: "tvos", oldestSupportedVersion: "9.0")
     public static let watchOS: Platform = Platform(name: "watchos", oldestSupportedVersion: "2.0")
     public static let linux: Platform = Platform(name: "linux", oldestSupportedVersion: .unknown)
+    public static let android: Platform = Platform(name: "android", oldestSupportedVersion: .unknown)
 }
 
 /// Represents a platform version.

Sources/TSCUtility/Platform.swift

@@ -13,6 +13,7 @@ import Foundation
 
 /// Recognized Platform types.
 public enum Platform {
+    case android
     case darwin
     case linux(LinuxFlavor)
 
@@ -33,6 +34,10 @@ public enum Platform {
             if localFileSystem.isFile(AbsolutePath("/etc/debian_version")) {
                 return .linux(.debian)
             }
+            if localFileSystem.isFile(AbsolutePath("/system/bin/toolbox")) ||
+               localFileSystem.isFile(AbsolutePath("/system/bin/toybox")) {
+                return .android
+            }
         default:
             return nil
         }

Tests/PackageLoadingTests/PackageBuilderTests.swift

@@ -1376,6 +1376,7 @@ class PackageBuilderTests: XCTestCase {
             "ios": "8.0",
             "tvos": "9.0",
             "watchos": "2.0",
+            "android": "0.0",
         ]
 
         PackageBuilderTester(manifest, in: fs) { result in
@@ -1411,6 +1412,7 @@ class PackageBuilderTests: XCTestCase {
             "linux": "0.0",
             "ios": "8.0",
             "watchos": "2.0",
+            "android": "0.0",
         ]
 
         PackageBuilderTester(manifest, in: fs) { result in