Fix compilation of arm-wince on Linux(?).

rtl/arm/arm.inc & setjump.inc:
  * don't use BX if the current CPU (default for arm-wince is ARMv3)  does not support it


git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25393 3ad0048d-3df7-0310-abae-a5850022a9f2