kernel: fix segmentation fault in mconf on linux

Commit 86c966a8ae caused HOST_LOADLIBES to
include -lncurses. This was added for fixing build issues on macOS.
This introduces issues on Linux when wide-character ncurses is being
used for compiling, but the non-wide-character version is linked in.

Fix this by adding the extra override for HOST_LOADLIBES only on macOS.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

include/kernel-build.mk

@@ -159,7 +159,9 @@ define BuildKernel
 	rm -f $(LINUX_DIR)/.config.prev
 	rm -f $(STAMP_CONFIGURED)
 	$(LINUX_RECONF_CMD) > $(LINUX_DIR)/.config
-	$(_SINGLE)$(KERNEL_MAKE) HOST_LOADLIBES="-L$(STAGING_DIR_HOST)/lib -lncurses" $$@
+	$(_SINGLE)$(KERNEL_MAKE) \
+		$(if $(findstring Darwin,$(HOST_OS)),HOST_LOADLIBES="-L$(STAGING_DIR_HOST)/lib -lncurses") \
+		$$@
 	$(LINUX_RECONF_DIFF) $(LINUX_DIR)/.config > $(LINUX_RECONFIG_TARGET)
 
   install: $(LINUX_DIR)/.image