RFR(XS): 8144930: gcc 4.1.2: fix build flags after "8114853 variable tracking size limit exceeded"

[Lindenmaier, Goetz]

Hi,

Please review and sponsor this tiny fix for the build with gcc 4.1.2.
I would appreciate if this would be pushed before 8114853 moves
on to jdk9/hs.
http://cr.openjdk.java.net/~goetz/webrevs/8144930-vmStructs/webrev.00/

Best regards,
  Goetz.