arm: setjmp/longjmp: fix PIC vs SHARED thinkos

The logic in setjmp/__longjmp incorrectly uses "PIC" to figure out
whether the code is going into a shared library when it should be
using "SHARED".  If you build glibc with a gcc version that has PIE
enabled by default, then the code will try to use symbols that are
only in the shared library.

URL: https://bugs.gentoo.org/336914