add USE_PROFILER to Cmake

[oxarbitrage]

Core developer @abitmore had been using sucessfully some profiling with gprof in our binaries at different scenarios for example #1113

this pull adds the option to compile with profile information by cmake, something as:

cmake -DBOOST_ROOT="$BOOST_ROOT" -DCMAKE_BUILD_TYPE=RelWithDebInfo -DUSE_PROFILER=ON .

This option is off by default as the binary will be much more slower when adding profiling info. The use of gprof is outside of the scope, option should be used by an experienced developer interested in project performance.

A note written in #1140:

• need cmake output msg that build will be made with profile.

[abitmore]

Thanks.
My local setup has this, I'm not sure if it's necessary though:

         if ( FULL_STATIC_BUILD )
-          set( CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static-libstdc++ -static-libgcc")
+          set( CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static-libstdc++ -static-libgcc -pg")
         endif ( FULL_STATIC_BUILD )

[oxarbitrage]

i actually had that too in my initial setup but then confirmed it is not needed, the gmon.out is generated without it and gprof just works fine.

[pmconrad]

• IMO this will get messy if more such options are added in the future. Better keep the original line and only add "-pg" if USE_PROFILER is ON.
• Perhaps add -pg to CMAKE_C_FLAGS not only CMAKE_CXX_FLAGS?

[oxarbitrage]

IMO this will get messy if more such options are added in the future. Better keep the original line and only add "-pg" if USE_PROFILER is ON.

changed this.

Perhaps add -pg to CMAKE_C_FLAGS not only CMAKE_CXX_FLAGS?

I made some tests with this and also by adding pg to the linker flags before. I am not an expert in profiling, actually my first time checking this out but i think they don't make any difference.

Still things to be done