cmake remove circular linking and reorganize

- px4_add_module now requires MAIN
 - px4_add_library doesn't automatically link

src/platforms/posix/tests/hello/CMakeLists.txt

@@ -38,6 +38,4 @@ px4_add_module(
 		hello_start_posix.cpp
 		hello_example.cpp
 	DEPENDS
-		platforms__common
 	)
-# vim: set noet ft=cmake fenc=utf-8 ff=unix : 

src/platforms/posix/tests/hrt_test/CMakeLists.txt

@@ -38,6 +38,4 @@ px4_add_module(
 		hrt_test_start_posix.cpp
 		hrt_test.cpp
 	DEPENDS
-		platforms__common
 	)
-# vim: set noet ft=cmake fenc=utf-8 ff=unix : 

src/platforms/posix/tests/muorb/CMakeLists.txt

@@ -38,6 +38,4 @@ px4_add_module(
 		muorb_test_start_posix.cpp
 		muorb_test_example.cpp
 	DEPENDS
-		platforms__common
 	)
-# vim: set noet ft=cmake fenc=utf-8 ff=unix : 

src/platforms/posix/tests/vcdev_test/CMakeLists.txt

@@ -38,6 +38,4 @@ px4_add_module(
 		vcdevtest_start_posix.cpp
 		vcdevtest_example.cpp
 	DEPENDS
-		platforms__common
 	)
-# vim: set noet ft=cmake fenc=utf-8 ff=unix :