Fix JIT for ARMv6 (i.e., no thumb support)
ARM JIT: use static configuration

The output of "/proc/cpuinfo" seems wrong for a Raspberry Pi running
the latest Raspian, because it claims ARMv6-compatible but also claims
"thumb" as a feature and 7 as the CPU architecture. Use the C compiler's
configuraton, instead, which is relatively straightforward and drops
code that will turn out to be dead.