changes to build for ARM chromebook ubuntu 13.04 port

Minor changes were needed to get a pocl 'working' base on ARM chromebook, running ubuntu 13.04. With these changes, most of the short pocl tests pass on the Samsung series3 chromebook.

For armhf builds, there seemed to be mismatches on flags passed to LLC, CLANG etc, which have been corrected.

Currently, tested with the following configure line:
./configure --host=armv7l-unknown-linux-gnueabihf --enable-debug --disable-icd --enable-testsuites=all

More testing is appreciated!
ARM chromebook port: correct pocl-build.in for arm* targets.

changed the target for arm* by mistake; correcting it.
Fix 729 - x86 only should fail.
Fix compiler flags for ARM gnueabihf (i.e. Ubuntu 13.04).

Patch by Sumit Semwal. Thanks!