Support for Pinning or Mapping GCC/Glibc Versions in Dockcross Images (e.g. linux-armv7a-lts)

[JoriOtega]

Hi Dockcross team and community,

First, thank you for maintaining this cross-compilation environment. I’ve been using dockcross to build ARM32 Linux binaries, and it’s been very productive.

That said, I’m currently running into a need where toolchain version control matters — specifically the ability to use exact GCC versions (e.g., 8.3, 8.5, 9.x, or 10.x) with the corresponding glibc versions for better compatibility and reproducibility.

🔍 Problem
Right now, it’s difficult to determine which Dockcross image/tag/commit uses which version of:

• GCC
• glibc
• binutils

For example, the image dockcross/linux-armv7a-lts currently pulls in:

GCC 11.2.0 (via crosstool-NG 1.25.0)
glibc 2.36 (Debian)

However, this doesn’t match previous summaries or expectations, which mentioned GCC 8.5 and glibc 2.28.

💡 Use Case
I need to:

• [Important] Easily identify or pin a Dockcross image based on its toolchain
• Build software using specific GCC versions (8.3, 8.5, 9.x, 10.x)
• Maintain compatibility with a known glibc baseline
• Possibly build a custom dockcross variant (with known GCC/glibc)

This is particularly important for reproducible builds and CI pipelines that target legacy systems or constrained platforms.

✅ Feature Request / Suggestion
Would you consider:

• [Important] Publishing a version matrix or compatibility table (Docker image tag → GCC/glibc/binutils version)?
• Adding this information to the README.md or the image’s labels (LABEL metadata in Dockerfile)?
• Providing a clear method to override toolchain versions, such as:
• Using build-args
• Allowing custom crosstool-NG configs or overlays
• Documenting how to customize a toolchain while keeping dockcross structure

Thanks again for the excellent work. Looking forward to hearing what the maintainers and community think about this direction!