cmake remove circular linking and reorganize

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

src/lib/rc/CMakeLists.txt

@@ -30,17 +30,13 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 ############################################################################
-px4_add_module(
-	MODULE lib__rc
-	COMPILE_FLAGS
-		-Wno-unused-result
-	SRCS
-		st24.cpp
-		sumd.cpp
-		sbus.cpp
-		dsm.cpp
-		common_rc.cpp
-	DEPENDS
-		platforms__common
-	)
-# vim: set noet ft=cmake fenc=utf-8 ff=unix :
+
+add_library(rc
+	st24.cpp
+	sumd.cpp
+	sbus.cpp
+	dsm.cpp
+	common_rc.cpp
+)
+target_compile_options(rc PRIVATE -Wno-unused-result)
+target_link_libraries(rc PRIVATE prebuild_targets)

src/lib/rc/rc_tests/CMakeLists.txt

@@ -30,6 +30,7 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 ############################################################################
+
 px4_add_module(
 	MODULE lib__rc__rc_tests
 	MAIN rc_tests
@@ -38,7 +39,5 @@ px4_add_module(
 	SRCS
 		RCTest.cpp
 	DEPENDS
-		platforms__common
+		rc
 	)
-
-# vim: set noet ft=cmake fenc=utf-8 ff=unix :