[openwrt/openwrt] iproute2: point KERNEL_INCLUDE to toolchain headers

[LEDE Commits]

jogo pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/d015a39dd39fe5178f1be3d5e7cee9368d4f9935

commit d015a39dd39fe5178f1be3d5e7cee9368d4f9935
Author: Jonas Gorski <jonas.gorski at gmail.com>
AuthorDate: Wed Jun 18 10:46:35 2025 +0200

    iproute2: point KERNEL_INCLUDE to toolchain headers
    
    Glibc since 2.41 tries to include linux/sched/types.h from sched.h, and
    pointing KERNEL_INCLUDE to the kernel headers makes it use
    linux/sched/types.h from the kernel headers instead of the installed
    one.
    
    This then breaks the configure (test) compile for setns() and the test:
    
    mips-openwrt-linux-gnu-gcc -I/fork.openwrt/build_dir/target-mips_24kc_glibc/linux-ath79_generic/linux-6.6.93/include/uapi -o config.HaAJYe/setnstest config.HaAJYe/setnstest.c
    In file included from /fork.openwrt/build_dir/target-mips_24kc_glibc/linux-ath79_generic/linux-6.6.93/include/uapi/linux/sched/types.h:5,
                     from /fork.openwrt/staging_dir/toolchain-mips_24kc_gcc-14.3.0_glibc/include/bits/sched.h:63,
                     from /fork.openwrt/staging_dir/toolchain-mips_24kc_gcc-14.3.0_glibc/include/sched.h:43,
                     from config.HaAJYe/setnstest.c:2:
    /fork.openwrt/build_dir/target-mips_24kc_glibc/linux-ath79_generic/linux-6.6.93/include/uapi/linux/types.h:10:2: warning: #warning "Attempt to use kernel headers from user space, see https://kernelnewbies.org/KernelHeaders" [-Wcpp]
       10 | #warning "Attempt to use kernel headers from user space, see https://kernelnewbies.org/KernelHeaders"
          |  ^~~~~~~
    In file included from /fork.openwrt/build_dir/target-mips_24kc_glibc/linux-ath79_generic/linux-6.6.93/include/uapi/linux/posix_types.h:5,
                     from /fork.openwrt/build_dir/target-mips_24kc_glibc/linux-ath79_generic/linux-6.6.93/include/uapi/linux/types.h:14:
    /fork.openwrt/build_dir/target-mips_24kc_glibc/linux-ath79_generic/linux-6.6.93/include/uapi/linux/stddef.h:5:10: fatal error: linux/compiler_types.h: No such file or directory
        5 | #include <linux/compiler_types.h>
          |          ^~~~~~~~~~~~~~~~~~~~~~~~
    compilation terminated.
    
    Fix this by pointing KERNEL_INCLUDE to the toolchain headers, which
    include the installed kernel headers.
    
    Tested with musl, glibc, and SDK.
    
    Fixes: 60738feded ("iproute2: Fix KERNEL_INCLUDE in SDK")
    Reported-by: Signed-off-by: Konstantin Demin <rockdrilla at gmail.com>
    Signed-off-by: Jonas Gorski <jonas.gorski at gmail.com>
---
 package/network/utils/iproute2/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/network/utils/iproute2/Makefile b/package/network/utils/iproute2/Makefile
index 6a172d2abe..6a1b15e148 100644
--- a/package/network/utils/iproute2/Makefile
+++ b/package/network/utils/iproute2/Makefile
@@ -170,7 +170,7 @@ TARGET_LDFLAGS += -Wl,--as-needed
 TARGET_CPPFLAGS += -I$(STAGING_DIR)/usr/include/libnl-tiny
 
 MAKE_FLAGS += \
-	KERNEL_INCLUDE="$(LINUX_DIR)/include/uapi" \
+	KERNEL_INCLUDE="$(TOOLCHAIN_ROOT_DIR)/usr/include" \
 	SHARED_LIBS=$(SHARED_LIBS) \
 	IP_CONFIG_TINY=$(IP_CONFIG_TINY) \
 	BUILD_VARIANT=$(BUILD_VARIANT) \