SwiftDriver: forward -sysroot provided by the user

Sources/SwiftDriver/Jobs/GenericUnixToolchain+LinkerSupport.swift

@@ -218,9 +218,12 @@ extension GenericUnixToolchain {
       }
 
       if targetTriple.environment == .android {
-        if let sysroot = try getAndroidNDKSysrootPath() {
-          commandLine.appendFlag("--sysroot")
-          commandLine.appendPath(sysroot)
+        if let sysroot = parsedOptions.getLastArgument(.sysroot)?.asSingle {
+          commandLine.appendFlag("-sysroot")
+          try commandLine.appendPath(VirtualPath(path: sysroot))
+        } else if let sysroot = AndroidNDK.getDefaultSysrootPath(in: self.env) {
+          commandLine.appendFlag("-sysroot")
+          try commandLine.appendPath(VirtualPath(path: sysroot.pathString))
         }
       } else if let path = targetInfo.sdkPath?.path {
         commandLine.appendFlag("--sysroot")

Sources/SwiftDriver/Toolchains/GenericUnixToolchain.swift

@@ -14,6 +14,34 @@ import protocol TSCBasic.FileSystem
 import struct TSCBasic.AbsolutePath
 import var TSCBasic.localFileSystem
 
+internal enum AndroidNDK {
+  internal static func getOSName() -> String? {
+    // The NDK is only available on macOS, linux and windows hosts currently.
+#if os(Windows)
+    "windows"
+#elseif os(Linux)
+    "linux"
+#elseif os(macOS)
+    "darwin"
+#else
+    nil
+#endif
+  }
+
+  internal static func getDefaultSysrootPath(in env: [String:String]) -> AbsolutePath? {
+    // The NDK is only available on an x86_64 hosts currently.
+#if arch(x86_64)
+    guard let ndk = env["ANDROID_NDK_ROOT"], let os = getOSName() else { return nil }
+    return try? AbsolutePath(validating: ndk)
+      .appending(components: "toolchains", "llvm", "prebuilt")
+      .appending(component: "\(os)-x86_64")
+      .appending(component: "sysroot")
+#else
+    return nil
+#endif
+  }
+}
+
 /// Toolchain for Unix-like systems.
 public final class GenericUnixToolchain: Toolchain {
   public let env: [String: String]
@@ -118,48 +146,19 @@ public final class GenericUnixToolchain: Toolchain {
     return "libclang_rt.\(sanitizer.libraryName)-\(targetTriple.archName)\(environment).a"
   }
 
-  private func getAndroidNDKHostOSSuffix() -> String? {
-#if os(Windows)
-    "windows"
-#elseif os(Linux)
-    "linux"
-#elseif os(macOS)
-    "darwin"
-#else
-    // The NDK is only available on macOS, linux and windows hosts.
-    nil
-#endif
-  }
-
-  func getAndroidNDKSysrootPath() throws -> AbsolutePath? {
-#if arch(x86_64)
-    // The NDK's sysroot should be specified in the environment.
-    guard let ndk = env["ANDROID_NDK_ROOT"],
-          let osSuffix = getAndroidNDKHostOSSuffix() else {
-      return  nil
-    }
-    var sysroot: AbsolutePath =
-        try AbsolutePath(validating: ndk)
-            .appending(components: "toolchains", "llvm", "prebuilt")
-            .appending(component: "\(osSuffix)-x86_64")
-            .appending(component: "sysroot")
-    return sysroot
-#else
-    // The NDK is only available on an x86_64 host.
-    return nil
-#endif
-  }
-
   public func addPlatformSpecificCommonFrontendOptions(
     commandLine: inout [Job.ArgTemplate],
     inputs: inout [TypedVirtualPath],
     frontendTargetInfo: FrontendTargetInfo,
     driver: inout Driver
   ) throws {
     if driver.targetTriple.environment == .android {
-      if let sysroot = try getAndroidNDKSysrootPath() {
+      if let sysroot = driver.parsedOptions.getLastArgument(.sysroot)?.asSingle {
+        commandLine.appendFlag("-sysroot")
+        try commandLine.appendPath(VirtualPath(path: sysroot))
+      } else if let sysroot = AndroidNDK.getDefaultSysrootPath(in: self.env) {
         commandLine.appendFlag("-sysroot")
-        commandLine.appendFlag(sysroot.pathString)
+        try commandLine.appendPath(VirtualPath(path: sysroot.pathString))
       }
     }
   }

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -7929,7 +7929,65 @@ final class SwiftDriverTests: XCTestCase {
       ]))
     }
   }
-
+
+  func testAndroidNDK() throws {
+    try withTemporaryDirectory { path in
+      do {
+        let sysroot = path.appending(component: "sysroot")
+        var driver = try Driver(args: [
+          "swiftc", "-target", "aarch64-unknown-linux-android", "-sysroot", sysroot.pathString, #file
+        ])
+        let jobs = try driver.planBuild().removingAutolinkExtractJobs()
+        let frontend = try XCTUnwrap(jobs.first)
+        XCTAssertTrue(frontend.commandLine.contains(subsequence: [
+          .flag("-sysroot"),
+          .path(.absolute(sysroot))
+        ]))
+      }
+
+      do {
+        var env = ProcessEnv.vars
+        env["ANDROID_NDK_ROOT"] = path.appending(component: "ndk").nativePathString(escaped: false)
+
+        let sysroot = path.appending(component: "sysroot")
+        var driver = try Driver(args: [
+          "swiftc", "-target", "aarch64-unknown-linux-android", "-sysroot", sysroot.pathString, #file
+        ], env: env)
+        let jobs = try driver.planBuild().removingAutolinkExtractJobs()
+        let frontend = try XCTUnwrap(jobs.first)
+        XCTAssertTrue(frontend.commandLine.contains(subsequence: [
+          .flag("-sysroot"),
+          .path(.absolute(sysroot))
+        ]))
+      }
+
+      do {
+        let sysroot = path.appending(component: "ndk")
+
+        var env = ProcessEnv.vars
+        env["ANDROID_NDK_ROOT"] = sysroot.nativePathString(escaped: false)
+
+#if os(Windows)
+        let os = "windows"
+#elseif os(macOS)
+        let os = "darwin"
+#else
+        let os = "linux"
+#endif
+
+        var driver = try Driver(args: [
+          "swiftc", "-target", "aarch64-unknown-linux-android", #file
+        ], env: env)
+        let jobs = try driver.planBuild().removingAutolinkExtractJobs()
+        let frontend = try XCTUnwrap(jobs.first)
+        XCTAssertTrue(frontend.commandLine.contains(subsequence: [
+          .flag("-sysroot"),
+          .path(.absolute(sysroot.appending(components: "toolchains", "llvm", "prebuilt", "\(os)-x86_64", "sysroot"))),
+        ]))
+      }
+    }
+  }
+
   func testEmitAPIDescriptorEmitModule() throws {
     try withTemporaryDirectory { path in
       do {