uboot-zynq: disable mkeficapsule host tool

Since the bump to 2026.04, tools/Kconfig defaults TOOLS_MKEFICAPSULE to
y whenever EFI_LOADER is set, which the Zynq configs enable. The host
tool includes <gnutls/gnutls.h>, which the build system does not
provide, so the package fails to compile. Disable the tool, as the
other U-Boot packages carrying an EFI_LOADER config already do.

Fixes: d51c611e71 ("uboot-zynq: bump to 2026.04")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>

package/boot/uboot-zynq/Makefile

@@ -61,6 +61,10 @@ UBOOT_TARGETS := \
 	zybo \
 	zybo_z7
 
+# mkeficapsule host tool is disabled
+# due to a host-side GnuTLS dependency
+UBOOT_CUSTOMIZE_CONFIG := --disable TOOLS_MKEFICAPSULE
+
 define Build/InstallDev
 	$(INSTALL_DIR) $(STAGING_DIR_IMAGE)
 	$(CP) $(PKG_BUILD_DIR)/spl/boot.bin $(STAGING_DIR_IMAGE)/$(BUILD_DEVICES)-boot.bin