Fixes compilation on Linux.

RxBlocking/RunLoopLock.swift

@@ -11,11 +11,28 @@ import Foundation
     import RxSwift
 #endif
 
+typealias AtomicInt = Int32
+
+#if os(Linux)
+  func AtomicIncrement(increment: UnsafeMutablePointer<AtomicInt>) -> AtomicInt {
+      increment.memory = increment.memory + 1
+      return increment.memory
+  }
+
+  func AtomicDecrement(increment: UnsafeMutablePointer<AtomicInt>) -> AtomicInt {
+      increment.memory = increment.memory - 1
+      return increment.memory
+  }
+#else
+  let AtomicIncrement = OSAtomicIncrement32
+  let AtomicDecrement = OSAtomicDecrement32
+#endif
+
 class RunLoopLock {
     let currentRunLoop: CFRunLoopRef
 
-    var calledRun: Int32 = 0
+    var calledRun: AtomicInt = 0
-    var calledStop: Int32 = 0
+    var calledStop: AtomicInt = 0
 
     init() {
         currentRunLoop = CFRunLoopGetCurrent()
@@ -37,7 +54,7 @@ class RunLoopLock {
     }
 
     func stop() {
-        if OSAtomicIncrement32(&calledStop) != 1 {
+        if AtomicIncrement(&calledStop) != 1 {
             return
         }
         CFRunLoopPerformBlock(currentRunLoop, kCFRunLoopDefaultMode) {
@@ -47,7 +64,7 @@ class RunLoopLock {
     }
 
     func run() {
-        if OSAtomicIncrement32(&calledRun) != 1 {
+        if AtomicIncrement(&calledRun) != 1 {
             fatalError("Run can be only called once")
         }
         CFRunLoopRun()