Refactor: extract code to make an fd non-clocking into a function.

Simply extract part of the code from evtloopunix.cpp into a reusable
wxPipe::MakeNonBlocking() function to be able to reuse it elsewhere.

See #12636.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65992 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/unix/pipe.h

@@ -52,6 +52,16 @@ public:
         return true;
     }
 
+    // switch the given end of the pipe to non-blocking IO
+    bool MakeNonBlocking(Direction which)
+    {
+        const int flags = fcntl(m_fds[which], F_GETFL, 0);
+        if ( flags == -1 )
+            return false;
+
+        return fcntl(m_fds[which], F_SETFL, flags | O_NONBLOCK) == 0;
+    }
+
     // return TRUE if we were created successfully
     bool IsOk() const { return m_fds[Read] != INVALID_FD; }