shell-quote-argument escapes '='

[R. Diez]

Hallo all:

I am running a self-compiled Emacs version 26.2 on Ubuntu 18.04.4 LTS. I 
normally use Bash as a shell.

When I evaluate the following in Emacs:

  (shell-quote-argument "a=b")

I get:

  "a\\=b"

That's wrong, because it does not work in Bash:

  $ echo "a\\=b"
  a\=b

But even if I am getting confused with Emacs' string escaping, echo "a\=b" does 
not work either.

I am looking for the equivalent in Emacs for Bash' printf "%q" escaping/quoting:

  $ printf "%q" "a=b"
  a=b

I though I might just copy and modify shell-quote-argument, but it is too 
complicated for my limited Lisp skills.

I do not need any flexibility or configuration, I just need to emulate the 
behaviour of Bash' printf "%q".

Thanks in advance for any help,
  rdiez