[Bug target/79712] Clang smarter about unrolling in fhourstones benchmark

[tulipawn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79712

--- Comment #6 from PeteVine <tulipawn at gmail dot com> ---
The difference between clang and gcc is even greater on ARMv7 Cortex A5 but
there's no way to catch up through unrolling (no effect): 

gcc version 7.0.1 20170225:    1227.2 Kpos/sec
clang 3.6:                     1540.4 Kpos/sec