Don't run each functional test in a different process

cmake/gtest/px4_add_gtest.cmake

@@ -111,8 +111,7 @@ function(px4_add_functional_gtest)
 		add_test(NAME ${TESTNAME}
 		         # functional tests need to run in a new process for each test,
 		         # since they set up and tear down system components
-		         COMMAND ${PX4_SOURCE_DIR}/Tools/run-gtest-isolated.py ${TESTNAME}
-		         WORKING_DIRECTORY ${PX4_BINARY_DIR})
+		         COMMAND ${PX4_BINARY_DIR}/${TESTNAME})
 
 		# attach it to the unit test target
 		add_dependencies(test_results ${TESTNAME})