[build] E: Link libnvx_crt0.a into test ELF

[esaurez]

Summary

nanvix/nanvix#2453 (already upstream) moved the _start entry point out of libposix.a into a new libnvx_crt0.a. Add libnvx_crt0.a to the test ELF link line so the linker resolves _start from it; without this the linker silently picks newlib's weak default _start and the test hangs at startup with no diagnostic output.

Dependencies

This PR assumes the following have already merged and the toolchain image has been republished:

• nanvix/nanvix#2487 — sys-ffi crate split that removes the duplicate __kcall_* / _do_exit_thread / _do_start_thread strong symbols from libnvx_crt0.a.
• nanvix/newlib#17 — declares newlib's _do_start as .weak so libnvx_crt0's strong SSE-aligned override wins cleanly without -Wl,--allow-multiple-definition.
• nanvix/toolchain-gcc#14 — pins the new newlib commit and triggers a republish of ghcr.io/nanvix/toolchain-gcc.

If those have not landed, the link line will fail with multiple definition of __kcall_* errors against the unpatched toolchain image.

What changes

One line added to the test ELF link line: $(SYSROOT_PATH)/lib/libnvx_crt0.a placed inside the existing --start-group ahead of libposix.a, so the linker resolves _start from libnvx_crt0's strong symbol.

[Copilot]

Pull request overview

This PR updates the Nanvix build/test integration for this libxml2 repo. It adds libnvx_crt0.a to the test ELF link to ensure the correct _start is pulled on post-PR-11b sysroots, and it also expands the build to produce a shared libxml2.so plus packaging targets.

Changes:

• Add libnvx_crt0.a (via $(wildcard ...)) to the test ELF link group and add --allow-multiple-definition to work around current duplicate symbols.
• Extend the Nanvix build to produce .libs/libxml2.so from the PIC objects in .libs/libxml2.a, and add validation checks for the shared library in test-functional.
• Add package / verify-package targets and adjust clean behavior (but removes prior install/staging behavior).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
.nanvix/z.py	Updates tracked Docker copy-back outputs and staged artifacts list to include libxml2.so.
.nanvix/Makefile.nanvix	Updates build/test rules: links libnvx_crt0.a into test ELF, adds .so build/validation, introduces packaging targets, and changes staging/clean behavior.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

[esaurez]

All prior review comments on this PR are stale and have been superseded by a rework.

The PR was originally filed as a much larger change that included Wave 3 .so build content plus a forward/backward-compat shim ($(wildcard ...) around libnvx_crt0.a, -Wl,--allow-multiple-definition as a safety flag, install/staging rework). All review comments above were filed against that larger version.

The PR has now been re-scoped to a single straightforward change: add libnvx_crt0.a to the test ELF link line (no wildcard, no safety flag). The diff is now 1-2 lines on a single file (see Files changed tab). The rework was done because we are only landing this work after Wave 1 + Wave 2 are fully merged and the toolchain image republished -- which makes all of the forward-compat machinery unnecessary.

Marking the prior comments as obsolete. If anything in the current 1-line diff still warrants discussion, please file a fresh comment.