static link libstdc++

The libstdc++6 versions can cary much more dramatically than the libc6
versions on a given system, so statically link them.

CMakeLists.txt

@@ -97,6 +97,7 @@ else()
         Backward::Backward
     )
 endif()
+target_link_options(spectatord_main PRIVATE "-static-libstdc++")
 
 #-- metrics_gen executable
 add_executable(metrics_gen