Fix linking error visible in conda: undefined reference to clock_gettime

Author: oshadura

cmake/modules/AddRootBench.cmake

@@ -43,7 +43,7 @@ function(RB_ADD_GBENCHMARK benchmark)
   # FIXME: For better coherence we could restrict the libraries the test suite could link
   # against. For example, tests in Core should link only against libCore. This could be tricky
   # to implement because some ROOT components create more than one library.
-  target_link_libraries(${benchmark} ${ARG_LIBRARIES} gbenchmark RBSupport)
+  target_link_libraries(${benchmark} ${ARG_LIBRARIES} gbenchmark RBSupport rt)
   #ROOT_PATH_TO_STRING(mangled_name ${benchmark} PATH_SEPARATOR_REPLACEMENT "-")
   #ROOT_ADD_TEST(gbench${mangled_name}
   #  COMMAND ${benchmark}
@@ -180,7 +180,7 @@ function(RB_GENERATE_DICTIONARY dictname)
       list(APPEND FULL_PATH_HEADERS ${CMAKE_CURRENT_SOURCE_DIR}/${hdr})
     endif()
   endforeach()
-  
+
   ROOT_GENERATE_DICTIONARY(${dictname} ${FULL_PATH_HEADERS}
                            MODULE ${dictname}
                            LINKDEF ${ARG_LINKDEF}