Update top level cmake to avoid build failure

[Andreachen0707]

In top level cmake, we have: set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wno-write-strings -Wno-deprecated-declarations") # -std=c++14 should this be modified to
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wno-write-strings -Wno-error") # -std=c++14

If user has CMAKE_CXX_FLAGS set as -Werror, then jetson-inference will not be able to build. Only deprecated-declarations seems not able to capture all the warning in jetson-inference, there are also unused-parameter etc.