bug fix in darhsan-config linker options

Since we had to modify HDF5/PnetCDF linker flags to work on Cray
by undefining appropriate symbols, we need to update the linker
options used in darshan-config. darshan-config linker options need
to include the stubs libraries and use '--start-group' and
'--end-group' flags to resolve the symbols correctly

darshan-runtime/darshan-config.in

@@ -12,7 +12,7 @@ DARSHAN_LD_FLAGS="@LDFLAGS@"
 #   in turn used one of those HLLs).
 
 PRE_LD_FLAGS="-L$DARSHAN_LIB_PATH $DARSHAN_LD_FLAGS -ldarshan -lz -Wl,@$DARSHAN_SHARE_PATH/ld-opts/darshan-base-ld-opts"
-POST_LD_FLAGS="-L$DARSHAN_LIB_PATH -ldarshan -lz -lrt -lpthread"
+POST_LD_FLAGS="-L$DARSHAN_LIB_PATH -Wl,--start-group -ldarshan -ldarshan-stubs -Wl,--end-group -lz -lrt -lpthread"
 
 usage="\
 Usage: darshan-config [--pre-ld-flags] [--post-ld-flags]"