output_limit: use add_library instead of px4_add_library

px4_add_library adds uorb dependencies, which since cf26f24387 added libm.
This in turn led to build failures for px4_io-v2 in the form of:
__aeabi_f2d' wf_sqrt.c:(.text.sqrtf+0x54): undefined reference to
__aeabi_ddiv'

src/lib/output_limit/CMakeLists.txt

@@ -31,4 +31,6 @@
 #
 ############################################################################
 
-px4_add_library(output_limit output_limit.cpp)
+add_library(output_limit output_limit.cpp)
+target_link_libraries(output_limit PRIVATE prebuild_targets)
+