For anyone coming across this later, you can do something like this in your CMakeLists.txt to get it to find the correct variables with a system installed version of argus.
find_path(ARGUS_INCLUDE_DIR Argus/Argus.h
HINTS "/usr/src/jetson_multimedia_api/argus/include")
set(CMAKE_MODULE_PATH "/usr/src/jetson_multimedia_api/argus/cmake" "${CMAKE_MODULE_PATH}")
find_package(Argus REQUIRED)
You probably also will want to include the headers as SYSTEM headers to avoid a ton of pedantic warnings:
include_directories(
SYSTEM ${ARGUS_INCLUDE_DIR}
)