Flatpak's fail to build on non-glibc systems due to executing glibc-linked binaries on the host context

[PureTryOut]

Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a bug that matches the one I want to file, without success.

flatpak-builder version

1.4.7

Flatpak version

1.16.1

How to reproduce

1. Get a Musl libc-based system like Alpine Linux or postmarketOS
2. Build a Flatpak, I'm using this Flutter app as an example

Expected Behavior

Every binary ran during build to be ran in the sandbox so it can be compiled anywhere.

Actual Behavior

Binaries are ran on the host, which fails on non-glibc systems. In the example given in the "How to reproduce section" the following is printed during the error:

Error: module flutter: Failed to execute child process “bsdunzip” (No such file or directory)

This bsdunzip comes from the Flutter build system and is linked against glibc, but that shouldn't be a problem when ran in the sandbox indicating this is ran in the host context instead.

Additional Information

I'm using the app I mentioned as an example now but I had the same problem with multiple other Flatpak's. Basically any application that requires running pre-compiled binaries fail on Musl-libc based systems.

[bbhtt]

I'm not sure if I understand this? flatpak-builder relies on bsdunzip from host to decompress zip files used in sources. Do you have bsdunzip installed on host?

This bsdunzip comes from the Flutter build system and is linked against glibc

Where?

[PureTryOut]

Ah, derp, that's me assuming things. You're right, it's not required by Flutter, I just though it was. Installing bsdunzip on my host fixed the problem, sorry for bothering you with this! I'll make sure the Alpine packaged version of flatpak-builder adds that dependency so others won't have the same problem.