Turn on frame pointer elimination

[brson]

We currently build C++ code and Rust with frame pointers on, though we don't actually use them for anything (intended for GC). This is overhead that C and C++ don't usually have so it would be nice to turn on elimination.

[graydon]

I think we'll need them for gc, fwiw

[thestinger]

@graydon: on Linux x86_64 we should be using the DWARFv3 Call Frame Information for walking the stack, although I have no idea if we're emitting it correctly right now (likely on OS X and FreeBSD too). We might be, because gdb uses it and seems to work.

[brson]

We'll leave it off until we have solutions for GC, which will probably end up being platform specific. libunwind should make it easy on linux and freebsd.

[brson]

Reopening because this caused a regression in #8833, so reverted in #8838