[llvm] [AIX] Remove unsupported AIX native echo option -n (PR #199079)

[via llvm-commits]

Himadhith wrote:

> @Himadhith, the PR description mentions something about using `\c`, but the PR changes don't seem to match?

First I tried to add `\c` but the test failed on linux build because linux does not recognise `\c` without the `-e` option passed to echo. But on AIX builtin echo `-e` was also not a supported option, so in the final code changes I had to modify it to use printf to have better portability. But the description remained to be explaining the previous changes, that's my bad. I will modify the description here, but do I need to revert the PR and make sure while merging in the PR the proper description is present?

https://github.com/llvm/llvm-project/pull/199079