Force code generation in assembly generation smoke-tests
In llvm/llvm-project@7b23f413d1 , `.text` started being suppressed from LLVM assembly in cases where it wasn't strictly necessary. Currently, the sample functions in these two tests are frequently decided to be IR-only functions, resulting in no code generation, so LLVM drops the `.text` directive.
Adding `#[no_mangle]` forces these tests back to their original intent - assembly code is generated, and so a `.text` directive is generated as well.
`@rustbot` label: +llvm-main
r? `@workingjubilee`
I'll attach a buildbot link once it finishes consuming this PR
030333a456