[openwrt/openwrt] 6rd: add CPPFLAGS

[LEDE Commits]

hauke pushed a commit to openwrt/openwrt.git, branch openwrt-25.12:
https://git.openwrt.org/da0b16367cb3e5bf591e9dab200358bc0a7db004

commit da0b16367cb3e5bf591e9dab200358bc0a7db004
Author: Hauke Mehrtens <hauke at hauke-m.de>
AuthorDate: Mon Feb 16 01:47:50 2026 +0100

    6rd: add CPPFLAGS
    
    Forward the OpenWrt CPPFLAGS to the compile process. This fixes fortify
    sources support.
    
    Link: https://github.com/openwrt/openwrt/pull/22056
    Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
    (cherry picked from commit b497c3f68f294df5111715a1465a204c12e38f05)
---
 package/network/ipv6/6rd/Makefile     | 1 +
 package/network/ipv6/6rd/src/Makefile | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/package/network/ipv6/6rd/Makefile b/package/network/ipv6/6rd/Makefile
index 3ab8198ef3..d4b65afb23 100644
--- a/package/network/ipv6/6rd/Makefile
+++ b/package/network/ipv6/6rd/Makefile
@@ -35,6 +35,7 @@ define Build/Compile
 	$(MAKE) -C $(PKG_BUILD_DIR) \
 		CC="$(TARGET_CC)" \
 		CFLAGS="$(TARGET_CFLAGS) -Wall" \
+		CPPFLAGS="$(TARGET_CPPFLAGS)" \
 		LDFLAGS="$(TARGET_LDFLAGS)"
 endef
 
diff --git a/package/network/ipv6/6rd/src/Makefile b/package/network/ipv6/6rd/src/Makefile
index 2881d43589..526ffcaeb0 100644
--- a/package/network/ipv6/6rd/src/Makefile
+++ b/package/network/ipv6/6rd/src/Makefile
@@ -1,7 +1,7 @@
 all: 6rdcalc
 
 6rdcalc: 6rdcalc.c
-	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $<
+	$(CC) $(CPPFLAGS) $(CFLAGS) $(LDFLAGS) -o $@ $<
 
 clean:
 	rm -f 6rdcalc