There is a new pull request by paper42 against master on the void-packages repository

https://github.com/paper42/void-packages xbps-src-fix-subpkg-avail
https://github.com/void-linux/void-packages/pull/37617

xbps-src: fix detecting subpackage availability
<!-- Uncomment relevant sections and delete options which are not applicable -->

#### Testing the changes
- I tested the changes in this PR: **briefly**

This is marked as draft because it doesn't work as expected in all cases, for example when a subpackage is added like in cryptsetup:
```sh
if [ "$XBPS_TARGET_LIBC" = musl ]; then
	configure_args+=" --enable-static-cryptsetup"
	subpackages+=" cryptsetup-static"
...
```

```sh
%: ./xbps-src show-avail cryptsetup-static; echo $?
0
```

fixes #37578

<!--
#### New package
- This new package conforms to the [quality requirements](https://github.com/void-linux/void-packages/blob/master/Manual.md#quality-requirements): **YES**|**NO**
-->

<!-- Note: If the build is likely to take more than 2 hours, please add ci skip tag as described in
https://github.com/void-linux/void-packages/blob/master/CONTRIBUTING.md#continuous-integration
and test at least one native build and, if supported, at least one cross build.
Ignore this section if this PR is not skipping CI.
-->
<!--
#### Local build testing
- I built this PR locally for my native architecture, (ARCH-LIBC)
- I built this PR locally for these architectures (if supported. mark crossbuilds):
  - aarch64-musl
  - armv7l
  - armv6l-musl
-->


A patch file from https://github.com/void-linux/void-packages/pull/37617.patch is attached