package/util-linux: fix non-MMU build

commit: https://gitlab.com/buildroot.org/buildroot/-/commit/d42fa9122749979e4e4226f85eca517fb64eb780
branch: https://gitlab.com/buildroot.org/buildroot/-/tree/master

Buildroot commit 31af509b4f4fe52f67bd9109b8732a55b8f9cd2d bumped the package from 2.40.2 to 2.41.1. This bump includes upstream commit
https://github.com/util-linux/util-linux/commit/a3f1255f1891ddbaf3bb6a32af28569c0e6f3b91
which was added to version 2.41 and includes the usage of pthread_atfork() causing build errors on non-MMU platforms:

libuuid/src/gen_uuid.c: In function 'uuid_generate_time_generic':
libuuid/src/gen_uuid.c:629:17: error: implicit declaration of function
'pthread_atfork'; did you mean 'pthread_join'? [-Wimplicit-function-declaration]
629 | pthread_atfork(NULL, NULL, reset_uuidd_cache);

The oldest build error of this kind can be found on the 2025.11.x branch with version 2.41.1:
https://autobuild.buildroot.net/results/87c/87c74435be14956fd45f730269eac102e70d56da/

The issue occurs because uClibc-ng is not very consistent with its pthread_atfork() definition: it doesn't provide a prototype for it on !MMU platforms (causing the build failure), but it does provide a stub implementation (causing the configure script to believe pthread_atfork is available). This issue was reported to upstream uClibc-ng at
https://mailman.openadk.org/mailman3/hyperkitty/list/[email protected]/thread/WEA7IQC3YAWTSFDHCLYRQJZTC4IUIY7J/.

A backport of this patch to the LTS branches should be considered, but probably not 2025.02.x as it uses version 2.40.x.

Fixes:
https://autobuild.buildroot.org/results/a21e81e64eccc866b575a4f3b1376c50f2ffd837/

---
 package/util-linux/util-linux.mk | 5 +++++
 1 file changed, 5 insertions(+)

index b4175024c4..807a9fb828 100644
@@ -136,6 +136,11 @@ UTIL_LINUX_CONF_ENV += CFLAGS="$(TARGET_CFLAGS) -Dstatic_assert=_Static_assert"
 UTIL_LINUX_CONF_ENV += LIBS="$(UTIL_LINUX_LINK_LIBS)"
 UTIL_LINUX_MAKE_OPTS += LIBS="$(UTIL_LINUX_LINK_LIBS)"
 
+# pthread support uses pthread_atfork, which is not available on nommu
+ifeq ($(BR2_USE_MMU),)
+UTIL_LINUX_CONF_ENV += ac_cv_lib_pthread_pthread_atfork=no
+endif
+
 ifeq ($(BR2_PACKAGE_LIBSELINUX),y)
 UTIL_LINUX_DEPENDENCIES += libselinux
 UTIL_LINUX_CONF_OPTS += --with-selinux

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