Second try to fix travis autotest adding x11 in macos packages

.travis.yml

@@ -73,6 +73,7 @@ matrix:
           - gawk
           - libxml++
           - qt5
+          - x11
 
 before_install:
   - source .travis/common.sh

vpr7_x2p/vpr/CMakeLists.txt

@@ -20,6 +20,7 @@ if (ENABLE_VPR_GRAPHICS)
   if (NOT X11_FOUND)
     message(WARNING "Failed to find required X11 library (on debian/ubuntu try 'sudo apt-get install libx11-dev' to install)")
     #Disable
+  else ()
     set(ENABLE_VPR_GRAPHICS false)
   endif()
 endif()