Fix build on Unix.

sleep(3) is defined on unistd.h, so you need to include it.

/home/thiago/src/qt/creator/src/plugins/android/androidconfigurations.cpp(556): error: identifier "sleep" is undefined

Change-Id: I71c76bd7f085240d9e3ceaad1ac062387cf7c838
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>

src/plugins/android/androidconfigurations.cpp

@@ -52,6 +52,8 @@
 #include <iostream>
 #include <windows.h>
 #define sleep(_n) Sleep(1000 * (_n))
+#else
+#include <unistd.h>
 #endif
 
 using namespace Utils;