Fixed SITL build (and clang posix build)

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

cmake/configs/posix_sitl_default.cmake

@@ -18,7 +18,6 @@ set(config_module_list
 	platforms/posix/drivers/gyrosim
 	platforms/posix/drivers/rgbledsim
 	platforms/posix/drivers/ledsim
-	platforms/posix/drivers/df_imu
 	systemcmds/param
 	systemcmds/mixer
 	systemcmds/ver

src/firmware/posix/CMakeLists.txt

@@ -30,7 +30,7 @@ else()
 		${CMAKE_SOURCE_DIR}/src/platforms/posix/main.cpp
 		apps.h
 		)
-	if (NOT ${CMAKE_C_COMPILER_ID} STREQUAL "Clang" AND NOT APPLE)
+	if (${CMAKE_C_COMPILER_ID} STREQUAL "Clang" AND NOT APPLE)
 		target_link_libraries(mainapp
 			-Wl,--start-group
 			${module_libraries}