examples/fdpicxip: Build the module fixtures without nuttx/tools/fdpic.

[casaroli]

Summary

The FDPIC fixtures this example and testing/fs/xipfs carry were built by an explicit make regen that reached into nuttx/tools/fdpic. Review of apache/nuttx#19940 asked that NuttX not carry a module build of its own, so the build moves here, beside the sources it builds.

They keep a build of their own because they are loader edge cases, not ordinary modules: a library with a SONAME, a module with more DT_NEEDED entries than the loader will follow, one whose imports stay in the lazy binding table, and one naming a symbol the firmware does not export. Application.mk cannot say -soname, or "no entry point", or "link against that other module".

The build uses the configured tree's module flags (CMODULEFLAGS, CXXMODULEFLAGS, LDMODULEFLAGS), linker script and crt0 source. Three things are pinned so the committed headers do not depend on how the tree is configured: the CPU (cortex-m3, so one set of headers runs on v7-M and v8-M), no debug information, and -Os. A library is compiled with default visibility, because the module flags hide every symbol and a library must export its functions.

fdpic-embed.py becomes xxd and a template. fdpic-verify.sh and nuttx-exports.sh go with no replacement: they checked at build time what the xipfs suite already asserts at run time.

depends-on: apache/nuttx/pull/20388
depends-on: apache/nuttx/pull/20368

Impact

make regen is not part of the application build, and the *_bin.h headers stay committed, so both apps still build with a plain toolchain and no FDPIC linker.

The headers are regenerated here. A fixture now starts in the tree's crt0, which needs apache/nuttx#20388 to run its constructors under FDPIC, and the library fixtures need apache/nuttx#20368. NUTTX_DIR has to be configured with CONFIG_FDPIC, and CONFIG_HAVE_CXXINITIALIZE decides whether crt0 runs constructors, so the headers were generated with it on.

Testing

mps2-an500:xipfs with CONFIG_FDPIC under QEMU, xipfs_test fdpic:

nuttx	fixtures	result
master	apps master	28 passed, 6 failed
master + #20388 + #20368	apps master	32 passed, 2 failed
master + #20388 + #20368	this PR	34 passed, 0 failed

Regenerating against a tree configured with CONFIG_DEBUG_NOOPT and against one with CONFIG_DEBUG_FULLOPT gives byte for byte the same headers.

tools/checkpatch.sh -c -u -m -g passes.

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• [5.5/10] arch/arm, cmake: Build FDPIC modules in the normal ELF build. nuttx#19940 @ c08569ce6e

CI run: https://github.com/apache/nuttx-apps/actions/runs/33193062300

[acassis]

@casaroli please include the CMakefile.txt too

[casaroli]

@casaroli please include the CMakefile.txt too

Done

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• [5.5/10] arch/arm, cmake: Build FDPIC modules in the normal ELF build. nuttx#19940 @ dfbab0c528

CI run: https://github.com/apache/nuttx-apps/actions/runs/34276056553

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• [7.5/10] arch/arm: Build a loadable module and a shared library as FDPIC too. nuttx#20360 @ 74d0b38156

CI run: https://github.com/apache/nuttx-apps/actions/runs/36120398868

[github-actions]

🔗 Cross-repo PR dependencies

The read-only Build run reported the following dependent PR(s) and fetched head SHA(s):

• [9.25/10] libs/libc/elf, arch/arm: Start an FDPIC module linked by the tree's module flags nuttx#20388 @ 8376df2a16
• [9/10] libs/libc/elf: Load the libraries a module names in DT_NEEDED nuttx#20368 @ 5fa42705b5

CI run: https://github.com/apache/nuttx-apps/actions/runs/36467652465