[common] cpuinfo: implement lgDebugCPU

This is a helper function that can be run at startup to quickly generate
a debug print containing CPU information.

common/CMakeLists.txt

@@ -33,6 +33,7 @@ set(COMMON_SOURCES
   src/runningavg.c
   src/ringbuffer.c
   src/vector.c
+  src/cpuinfo.c
 )
 
 add_library(lg_common STATIC ${COMMON_SOURCES})