add a workaround for fixing the stdbuf detection issue when building with clang

Signed-off-by: jchzhou <zhoujiacheng@iscas.ac.cn>
(cherry picked from commit 4787c1b0d7d83bd3716ce8b1ea414a2863149c6b)

coreutils.spec

@@ -1,6 +1,6 @@
 Name:       coreutils
 Version:    9.4
-Release:    6
+Release:    7
 License:    GPLv3+
 Summary:    A set of basic GNU tools commonly used in shell scripts
 Url:        https://www.gnu.org/software/coreutils/
@@ -87,7 +87,15 @@ autoreconf -fiv
 if [ %user = root ]; then
     export FORCE_UNSAFE_CONFIGURE=1
 fi
-export CFLAGS="$RPM_OPT_FLAGS -fno-strict-aliasing -fpic -fsigned-char"
+CFLAGS="$RPM_OPT_FLAGS -fno-strict-aliasing -fpic -fsigned-char"
+
+# add -Wno-unused-command-line-argument when building with clang
+# as a workaround for stdbuf detection faliure during configuring
+%if "%{?toolchain}" == "clang"
+CFLAGS="$CFLAGS -Wno-unused-command-line-argument"
+%endif
+
+export CFLAGS
 
 # make mknod work again in chroot without /proc being mounted
 export ac_cv_func_lchmod="no"
@@ -163,6 +171,9 @@ fi
 %{_mandir}/man*/*
 
 %changelog
+* Thu Jul 11 2024 jchzhou <zhoujiacheng@iscas.ac.cn> - 9.4-7
+- add a workaround for fixing clang building issues
+
 * Mon Jun 24 2024 huyubiao <huyubiao@huawei.com> - 9.4-6
 - backport patches from community