the legacy LLVM-style asm! syntax is no longer supported

Getting this error in my code:

```
error: the legacy LLVM-style asm! syntax is no longer supported
--> src\iaca.rs:14:9
|
14 | iaca_start_marker!();
| ^^^^^^^^^^^^^^^^^^^^^ help: replace with: `llvm_asm!`
|
= note: consider migrating to the new asm! syntax specified in RFC 2873
= note: alternatively, switch to llvm_asm! to keep your code working as it is
= note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more
info)

Start at the iaca_start_marker! invocation in src/iaca.rs:14 and inspect the macro implementation that expands to the legacy LLVM-style asm! syntax. Check the supported Rust inline-assembly syntax and verify the marker macro builds without this compiler error on the intended toolchain.

Written by the indexing model from the issue text.