Add a CMake build alongside autotools

[matejk]

Summary

Adds a CMake build (>= 3.18) that coexists with the autotools build, plus CI updates. Rebased onto the v2.4.8.4 release on main; 4 commits:

• VERSION file: the package version moves from AC_INIT to a top-level VERSION file read by both build systems, so there is a single source of truth. It tracks the release version (2.4.8.4), and the autotools PACKAGE_VERSION string is unchanged.
• Reusable message-compile script: messages/make_message_src.sh accepts optional source/output directories and honors $GENRB/$PKGDATA, so an out-of-source build can call it; the one-argument form keeps the historical behavior and messages/Makefile.am is unchanged.
• CI: a new workflow configures, builds, and runs ctest. Version updates for the existing workflows are in ci: update deprecated GitHub Actions versions #622.
• The CMake build itself.
• C11: a dedicated commit raises the CMake build to the C11 standard (gnu11).

Scope

Linux is fully wired: libltfs, the ltfs/mkltfs/ltfsck executables, the sg/file/itdtimg tape backends, both I/O schedulers, both key managers. macOS additionally builds the iokit tape backend. The FreeBSD/NetBSD backends are skipped with a notice and remain autotools-only. The build targets libfuse 2, matching autotools; the FUSE 3 selection follows as a small extension once #603 merges.

The CMake build compiles as C11 (gnu11, since LTFS uses _GNU_SOURCE/asprintf); a commented-out C17 line is provided for when the minimum supported toolchain is GCC 8+/Clang 7+.

Notable differences from the autotools implementation:

• ICU is found through CMake's ICU module instead of the icu-config tool that ICU removed in 2018 (ICU6x is set automatically for ICU >= 60); libxml2 uses find_package(LibXml2); fuse/uuid/net-snmp use pkg-config imported targets.
• The per-backend source symlinks and the CRC_OPTIMIZE rule are replaced by direct source paths and one SSE4.2-flagged OBJECT library.
• Plugins are MODULE libraries named exactly as ltfs.conf expects (libtape-sg.so etc.), installed to <libdir>/ltfs.
• Installed binaries and plugins keep the install libdir in their RUNPATH, as the libtool build does, unless it is a system directory; installs to /usr get no RUNPATH.
• ctest registers tests/t/*.sh by glob via the shared harness, so the build works with or without the integration test suite (Add an integration test suite using the file tape backend #611) and picks up its tests automatically.

Verification

Ubuntu VM: the CMake build and all 14 integration tests pass via ctest (with #611 merged alongside); the install tree matches autotools (bin, lib, plugins, etc/ltfs.conf{,.local}, pkgconfig, man, headers); ltfs --version reports the identical string; the autotools build and make check stay green. macOS 26 (arm64, macFUSE 5.2 SDK): the CMake build produces libltfs, the executables, and all plugins including libtape-iokit.so, as C11.

Fixes #521.

[vandelvan]

Hi @matejk ! Thanks for contributing, Just a small comment

[matejk]

Done, cmake.yml now uses actions/checkout@v6. The version updates for the existing workflows moved to a separate PR, #622.

[vandelvan]

LGTM! Thank you

[madjesc]

Hello @matejk thanks for this contribution.
Currently the default local build does not work in RHEL, as RHEL does not add local lib paths into ldconfig and they need to be configured within the system. Could you add the lib local install paths into the binary rpath? So it doesnt need configuration systemwide nor making symlinks

[madjesc]

[madjesc@lima-alma build]$ ldd /usr/local/bin/ltfs
	linux-vdso.so.1 (0x00007ffe43fa9000)
	libltfs.so.2 => not found
	libfuse.so.2 => /lib64/libfuse.so.2 (0x00007f2883c84000)
	libxml2.so.2 => /lib64/libxml2.so.2 (0x00007f2883afa000)
	libuuid.so.1 => /lib64/libuuid.so.1 (0x00007f2883af0000)
	libicuuc.so.67 => /lib64/libicuuc.so.67 (0x00007f2883905000)
	libicui18n.so.67 => /lib64/libicui18n.so.67 (0x00007f2883400000)
	libicuio.so.67 => /lib64/libicuio.so.67 (0x00007f28838f5000)
	libicudata.so.67 => /lib64/libicudata.so.67 (0x00007f2881800000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f2881400000)
	libz.so.1 => /lib64/libz.so.1 (0x00007f28838db000)
	liblzma.so.5 => /lib64/liblzma.so.5 (0x00007f28838ad000)
	libm.so.6 => /lib64/libm.so.6 (0x00007f28837d2000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f2883ccf000)
	libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f2881000000)
	libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f28837b5000)

[matejk]

Done. CMAKE_INSTALL_RPATH is now set to the install libdir unless that is a system directory, matching the libtool build (which embeds RUNPATH= into everything it installs). Installs to /usr get no RUNPATH, so deb/rpm packaging is unaffected.

Verified on Rocky 9: the stock install reproduces your ldd output; with the change ldd resolves /usr/local/lib64/libltfs.so.2 and ltfs --version runs. Note el9 uses /usr/local/lib64, not /usr/local/lib.

[madjesc]

LGTM overall.
Could you add the build directory into .gitignore? Most people build into build directory using cmake -S . -B build. So its nice to have a default gitignore entry for this directory

[matejk]

Done, /build/ is now in .gitignore.

[madjesc]

GTG 🔥☠️🔥