libelf: new recipe (elfutils carve-out) for Mesa radeonsi; wire into mesa

Mesa's radeonsi gallium driver requires libelf. Add a libelf recipe that builds
only the elfutils lib/+libelf/ subdirs (avoiding the libdw/libasm/tools glibc
surface) as a PIC static archive, relying on the new relibc headers/functions
(byteswap/error/libintl/ar/search + tsearch/mempcpy/rawmemchr). Installs
libelf.a + libelf.h/gelf.h/nlist.h + libelf.pc. Wired into mesa deps.

Verified: cook libelf - successful.

local/recipes/dev/libelf/recipe.toml

@@ -0,0 +1,77 @@
+[package]
+name = "libelf"
+# libelf only, carved out of elfutils. Mesa's radeonsi (AMD) gallium driver
+# requires libelf (dependency('libelf') / cc.find_library('elf')). We build just
+# the elfutils libelf sublibrary (+ its lib/ helper) rather than all of elfutils
+# (libdw/libasm/tools drag in a large glibc surface). Version tracks elfutils.
+version = "0.190"
+description = "libelf — ELF object file access library (from elfutils). Required by Mesa's radeonsi gallium driver."
+
+[source]
+tar = "https://sourceware.org/elfutils/ftp/0.190/elfutils-0.190.tar.bz2"
+
+[build]
+template = "custom"
+# libelf's lib/ helper (eu-config.h/system.h) pulls libintl.h, error.h,
+# byteswap.h — now provided by relibc — plus argp.h/obstack.h from the deps.
+dependencies = [
+    "zlib",
+    "argp-standalone",
+    "musl-obstack",
+    "musl-fts",
+]
+script = '''
+DYNAMIC_INIT
+
+# libelf links into radeonsi.so, so build a PIC static archive (baked in; no
+# extra runtime .so to ship). -fPIC + static. elfutils compiles with -Werror
+# and trips on -Wformat-nonliteral etc. under the Redox cross toolchain; drop
+# -Werror (also via --disable-werror below) so warnings are non-fatal.
+export CFLAGS="-fPIC -Wno-error ${CFLAGS:-}"
+
+# elfutils' configure autoconf checks assume a few glibc behaviours; force the
+# results that are correct for relibc so configure completes without running
+# target binaries.
+COOKBOOK_CONFIGURE_FLAGS+=(
+    --enable-static
+    --disable-shared
+    --disable-werror
+    --disable-nls
+    --disable-debuginfod
+    --disable-libdebuginfod
+    --disable-demangler
+    --without-zstd
+    --without-bzlib
+    --without-lzma
+    ac_cv_func_mempcpy=yes
+)
+
+# Configure (out-of-tree, in COOKBOOK_BUILD which is CWD), then build ONLY the
+# lib/ helper and libelf/, skipping libdw/libasm/backends/src (not needed and
+# glibc-heavy).
+"${COOKBOOK_CONFIGURE}" "${COOKBOOK_CONFIGURE_FLAGS[@]}"
+"${COOKBOOK_MAKE}" -C lib -j"${COOKBOOK_MAKE_JOBS}"
+"${COOKBOOK_MAKE}" -C libelf -j"${COOKBOOK_MAKE_JOBS}" libelf.a
+
+# Install libelf.a + public headers by hand (the libelf `install` target also
+# pulls the shared lib / versioning we skipped).
+mkdir -p "${COOKBOOK_STAGE}/usr/lib" "${COOKBOOK_STAGE}/usr/include" "${COOKBOOK_STAGE}/usr/lib/pkgconfig"
+cp libelf/libelf.a "${COOKBOOK_STAGE}/usr/lib/"
+cp "${COOKBOOK_SOURCE}/libelf/libelf.h" "${COOKBOOK_SOURCE}/libelf/gelf.h" "${COOKBOOK_SOURCE}/libelf/nlist.h" "${COOKBOOK_STAGE}/usr/include/"
+
+# Provide a pkg-config so Mesa's dependency('libelf') resolves (its
+# find_library('elf') fallback would also work, but the .pc is cheap).
+cat > "${COOKBOOK_STAGE}/usr/lib/pkgconfig/libelf.pc" <<PC
+prefix=/usr
+exec_prefix=\${prefix}
+libdir=\${prefix}/lib
+includedir=\${prefix}/include
+
+Name: libelf
+Description: ELF object file access library (elfutils)
+Version: 0.190
+Libs: -L\${libdir} -lelf
+Libs.private: -lz
+Cflags: -I\${includedir}
+PC
+'''

local/recipes/libs/mesa/recipe.toml

@@ -38,6 +38,10 @@ dependencies = [
     # is headers only), so depending on "libclc" here is sufficient.
     "libclc",
     "libdrm",
+    # radeonsi (AMD gallium) requires libelf to parse shader ELF; provided by
+    # our libelf recipe (elfutils libelf carve-out). Mesa resolves it via
+    # dependency('libelf') / cc.find_library('elf').
+    "libelf",
     "liborbital",
     "libwayland",
     "linux-kpi",

recipes/dev/libelf

@@ -0,0 +1 @@
+../../local/recipes/dev/libelf