uboot-tools: fix libyaml linker error

When we cross build uboot-tools, the dtc tool is still compiled for
the host. Therefore, we should not attempt to link the OpenWrt system
libraries. CPU architecture mismatch can lead to build errors.

Fixes: openwrt/openwrt#22924
Fixes: 5592565 ("uboot-tools: update to v2026.04")
Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Link: openwrt/openwrt#22927
Signed-off-by: Robert Marko <robimarko@gmail.com>

Author: DragonBluep

package/boot/uboot-tools/Makefile

@@ -82,7 +82,7 @@ MAKE_FLAGS += \
 	ARCH="sandbox" \
 	TARGET_CFLAGS="$(TARGET_CFLAGS)" \
 	TARGET_LDFLAGS="$(TARGET_LDFLAGS)" \
-	PKG_CONFIG_SYSROOT_DIR="$(STAGING_DIR)" \
+	PKG_CONFIG_SYSROOT_DIR="$(STAGING_DIR_HOST)" \
 	NO_PYTHON=1 \
 	V=$(if $(findstring c,$(OPENWRT_VERBOSE)),1,)