made it build on tvOS and watchOS

Sources/Core/Process+Execute.swift

@@ -1,4 +1,4 @@
-#if !os(iOS)
+#if !os(iOS) && !os(tvOS) && !os(watchOS)
 import NIO
 
 /// Different types of process output.
@@ -97,7 +97,7 @@ extension Process {
 
             // will be set to false when the program is done
             var running = true
-            
+
             // readabilityHandler doesn't work on linux, so we are left with this hack
             DispatchQueue.global().async {
                 while running {

Sources/Core/Thread+Async.swift

@@ -18,10 +18,10 @@ extension Thread {
     /// - parameters:
     ///     - work: Closure to be called on new thread.
     public static func async(_ work: @escaping () -> Void) {
-        if #available(macOS 10.12, iOS 10.0, *) {
+        if #available(macOS 10.12, iOS 10.0, tvOS 10.0, watchOS 3.0, *) {
             Thread.detachNewThread(work)
         } else {
-            fatalError("macOS 10.12/iOS 10.0 or later required to call Thread.async(_:)")
+            fatalError("macOS 10.12/iOS 10.0/tvOS 10.0/watchOS 3.0 or later required to call Thread.async(_:)")
         }
     }
 }

Tests/CoreTests/CoreTests.swift

@@ -3,15 +3,20 @@ import XCTest
 
 class CoreTests: XCTestCase {
     func testProcessExecute() throws {
+        #if !os(iOS) && !os(tvOS) && !os(watchOS)
         try XCTAssertEqual(Process.execute("/bin/echo", "hi"), "hi")
+        #endif
     }
 
     func testProcessExecuteCurl() throws {
+        #if !os(iOS) && !os(tvOS) && !os(watchOS)
         let res = try Process.execute("/usr/bin/curl", "--verbose", "https://vapor.codes")
         XCTAssertEqual(res.contains("<title>Vapor"), true)
+        #endif
     }
 
     func testProcessAsyncExecute() throws {
+        #if !os(iOS) && !os(tvOS) && !os(watchOS)
         let eventLoop = MultiThreadedEventLoopGroup(numberOfThreads: 1)
         var lastOutput: ProcessOutput?
         let status = try Process.asyncExecute("/bin/echo", "hi", on: eventLoop) { output in
@@ -26,10 +31,13 @@ class CoreTests: XCTestCase {
         } else {
             XCTFail("no output")
         }
+        #endif
     }
 
     func testProcessExecuteMissing() throws {
+        #if !os(iOS) && !os(tvOS) && !os(watchOS)
         XCTAssertThrowsError(try Process.execute("foo", "hi"), "hi")
+        #endif
     }
 
     func testBase64() {