Fix the STATIC_LIBRARY build for gcc-4.7 ia32
Fix the STATIC_LIBRARY build for gcc-4.7 ia32

The prefix for these special thunks changed from __i686 to __x86 between
gcc4.6 and 4.7.

Review URL: https://codereview.appspot.com/7145044

SVN-Revision: 1840

sigma-random/dynamorio,sigma-random/dynamorio,daksunt/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,AmesianX/dynamorio,daksunt/dynamorio,daksunt/dynamorio,code4bones/dynamorio,code4bones/dynamorio,daksunt/dynamorio,bl4ckic3/dynamorio,sigma-random/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,daksunt/dynamorio,sigma-random/dynamorio,bl4ckic3/dynamorio,code4bones/dynamorio,sigma-random/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,bl4ckic3/dynamorio,bl4ckic3/dynamorio