Please consider dumping the config.log files to stdout, for a failing
build, to have the relevant information of a build available for
debugging. Should only be done for the failing target.

the GCC packaging is doing that like:

         s=`cat status`; rm -f status; \
         if [ $$s -ne 0 ] && [ -z
"$$NO_CONFIG_LOG_DUMP$$NO_CONFIG_LOG_DUMPS" ]; then \
           for log in $$(find $(builddir) -name config.log); do \
             case "$$log" in */build/build-*|*/stage1-*|*/prev-*)
continue; esac; \
             echo LOGFILE START $$log; \
             cat $$log; \
             echo LOGFILE END $$log; \
           done; \
         fi; \
         test $$s -eq 0