On ELF, the text section is opened with ".text", on MachO with
".section __TEXT,__text".
Previously, on ELF this test was actually matching a GNU note
section, which is no longer emitted on Solaris starting with
LLVM 18.
Fixes https://github.com/rust-lang/rust/issues/120105.
Adds a basic assembly test checking that each target can produce assembly
and update the target tier policy to require this.
Signed-off-by: David Wood <david@davidtw.co>
