asterx1_gps: fixed example CMakeLists depending on gpsToolkitLibrary presence

src/examples/CMakeLists.txt

@@ -2,7 +2,10 @@
 ADD_EXECUTABLE(testasterx1 testasterx1.cpp)
 
 # edit the following line to add the necessary libraries
-TARGET_LINK_LIBRARIES(testasterx1 asterx1_gps asterx1_process)
+IF(gpstk_LIBRARY)
+  TARGET_LINK_LIBRARIES(testasterx1 asterx1_process)
+ENDIF(gpstk_LIBRARY)
+TARGET_LINK_LIBRARIES(testasterx1 asterx1_gps)
 
 #fast building
 # ADD_EXECUTABLE(testasterx1 testasterx1.cpp ../asterx1.cpp)