[build] E: Build lxml C extensions as .so

[esaurez]

Summary

Produce position-independent liblxml_etree.so and liblxml_elementpath.so alongside the existing static .a archives. The new .so files form an explicit DT_NEEDED chain on top of the libxml2 and libxslt shared-library ports:

liblxml_etree.so       -> DT_NEEDED libxslt.so, libxml2.so
liblxml_elementpath.so -> (leaf, no DT_NEEDED on the XML chain)

so a Python interpreter (or any other host executable) can dlopen liblxml_etree.so once and have the loader resolve libxslt.so and libxml2.so transitively. libposix / libc / libm symbols are left UND and bound at dlopen time against the host executable's .dynsym, matching the extension-module model used elsewhere on Nanvix.

What changes

File	Change
.nanvix/Makefile.nanvix	The existing static-library build (compiled with -fPIC since this port's first revision) is preserved unchanged. New .libs/liblxml_etree.so and .libs/liblxml_elementpath.so targets link the .so files manually via -shared -fPIC -nostdlib, setting DT_SONAME=<name>.so and emitting the cross-library DT_NEEDED edges by linking through -L. -lxslt -lxml2 (resolved against the upstream-released libxslt.so / libxml2.so). test-functional now sanity-checks each .so: presence, minimum size, DT_SONAME, DT_NEEDED chain (including the absence of any unintended deps), and that the lxml extension entry points (PyInit_etree, PyInit__elementpath) appear in .dynsym. package / verify-package ship the static archives plus both .so files.
.nanvix/z.py	Adds the two .so files to _staged_output_files() so release packages them.

Build-time dependency

This PR's shared link requires libxml2.so and libxslt.so release artifacts (from the companion libxml2 and libxslt PRs adding shared-library support) to satisfy the DT_NEEDED edges on the link line. The companion PRs should land first; once they have released artifacts, this PR's CI can be re-pointed at those releases in .nanvix/nanvix.toml.

Runtime dependencies

Only useful once these loader changes ship:

• nanvix/nanvix#2473 -- DT_RUNPATH + .init_array invocation.
• nanvix/nanvix#2478 -- diamond DT_NEEDED handling. The lxml chain forms a diamond at runtime via the two paths from liblxml_etree.so into libxml2.so.

[Copilot]

Pull request overview

This PR updates the Nanvix port build to produce position-independent shared objects (liblxml_etree.so, liblxml_elementpath.so) alongside the existing static archives, aiming to allow consumers (e.g., Python) to dlopen() lxml and rely on transitive DT_NEEDED resolution for libxml2/libxslt.

Changes:

• Add .so build targets for the lxml modules and link them as shared libraries.
• Add package / verify-package targets for producing and checking a release tarball.
• Update .nanvix/z.py to include the new .so artifacts in the staged output list and clarify build help text.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
.nanvix/Makefile.nanvix	Adds shared-library build outputs and packaging targets; modifies build/staging/clean behavior.
.nanvix/z.py	Updates staged output list to include .so artifacts and updates build docstrings/help text.

Comments suppressed due to low confidence (1)

.nanvix/Makefile.nanvix:57

• With the staging/install flow, OUT_DIR, LIB_OUT, and TEST_OUT (and related vars) are required inputs. Dropping them from _REQUIRED means make all can run with empty vars and attempt to create/copy into paths like /release/... depending on how the shell expands them. Restoring the previous required-variable list avoids unsafe default paths and produces clearer errors when invoking the Makefile directly.

# Ensure required variables are defined.
_REQUIRED := PLATFORM PROCESS_MODE MEMORY_SIZE NANVIX_HOME NANVIX_TOOLCHAIN
ifneq ($(filter-out clean,$(_NANVIX_GOALS)),)
  $(foreach v,$(_REQUIRED),\
    $(if $($v),,$(error Required variable $v not set))\
  )

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[Copilot]

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 2