Unable to omit unwind tables from binary when using ReleaseSmall + LLVM

[wooster0]

Zig Version

0.14.0-dev.2164+6b2c8fc68

Steps to Reproduce and Observed Behavior

$ cat x.zig
pub fn main() void {}
$ zig build-exe x.zig -fno-unwind-tables -OReleaseSmall
error: <inline asm>:1:3: this directive must appear between .cfi_startproc and .cfi_endproc directives
         .cfi_undefined %rip
         ^

$

Expected Behavior

Successful compilation.

[Rexicon226]

This is the line of inline asm that's causing this:

zig/lib/std/start.zig

Line 250 in e5f5229

\\ .cfi_undefined %%rip

added in f289b82

[alexrp]

I have an upcoming PR that improves the compiler's handling of unwind tables, including adding a builtin.unwind_tables decl. With that, we can more easily decide whether to emit the .cfi_undefined directive.

Similar fix is needed in clone().

[alexrp]

#22035 is the first step here. We'll need a zig1.wasm update before we can actually start using @import("builtin").unwind_tables in standard library code, though.