Add missing -m64 arguments to makefile
Add missing -m64 arguments to makefile

Before this change, doing "make test" on a 32-bit system fails when
building the tests rather than when running them, with the unexpected
error:

/usr/bin/ld: i386 architecture of input file `allocator.o64' is
incompatible with i386:x86-64 output

Review URL: http://codereview.chromium.org/3342008
cnbird1999/seccompsandbox,ericmckean/seccompsandbox,ericmckean/seccompsandbox,ericmckean/seccompsandbox,cnbird1999/seccompsandbox,cnbird1999/seccompsandbox