Gzip error when trying to install from source with OTP version

I can install Elixir from source like so with no issue: `asdf install elixir ref:v1.8.1`. However, when I try to install it from source with a specific OTP version, I get an error:
```sh
$asdf install elixir ref:v1.8.1-otp-21
=> Checking whether specified Elixir release/reference exists...
==> Downloading v1.8.1-otp-21 to /tmp/elixir_build_W70U1J/elixir-ref-v1.8.1-otp-21-src.tar.gz
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 133 0 133 0 0 636 0 --:--:-- --:--:-- --:--:-- 633
100 15 100 15 0 0 7 0 0:00:02 0:00:01 0:00:01 90
==> Making the release

gzip: stdin: not in gzip format
tar: Child returned status 1
tar: Error is not recoverable: exiting now
```

I already have OTP 21 installed via ASDF, so maybe I am misunderstanding compiling Elixir with the right OTP version and I don't need to specify that when compiling from source since it will use the OTP version I have installed but I am not sure about that. I assume I would have to specify the OTP version in the install command since it can download a file with the Elixir source for that specific OTP version.

Please correct me if I'm doing something wrong here. Thanks for all of your work on this great plugin!

Start by reproducing `asdf install elixir ref:v1.8.1-otp-21` and inspect the downloaded archive or response before extraction. Compare it with the successful `ref:v1.8.1` installation path; done means the OTP-specific reference is either installed correctly or produces a clear, actionable error.

Written by the indexing model from the issue text.