Fix ARM hardfloat detection in linux

See
  http://code.google.com/p/v8/issues/detail?id=2140
  https://chromiumcodereview.appspot.com/10713009

The original code fails to detect at run-time when compiled
with GCC 4.7, because the undefined behavior of casting
void to double, and the r0/r1 clobbered in assembly code
isn't reaching the use when compared to 1.0 in VFP reg.
In summary, the old code is incorrect and overkill, and the
new code fix it.

Change-Id: I6b63a4f9789e08089368e431a5553f482400725a