mozjs102: Fix the armel build, don't use simd-accel on i386+armhf

@smcv This finishes your !6 (closed). Your commits are unchanged, except that in the second "WIP" is removed and the part dropped that was already in c18c64ee.

I've changed your simd-accel patch to also disable it on i386 and armhf, where we don't have any SIMD instructions in our baseline (even some of our armhf buildds don't have NEON).

There's a new mozjs102 upstream release today so I'm going to prepare that update and push it to Salsa