build: test for 64-bit time_t only when a host build needs it

host-build.mk runs the YEAR_2038 compiler test while it parses, so every
package with a host build runs it on every make call, also for a target
build or a build that has nothing to do.

Add the result to HOST_CONFIGURE_ARGS without expanding it, so the test
runs only when the host build is configured.

Signed-off-by: John Crispin <john@phrozen.org>

include/host-build.mk

@@ -97,9 +97,7 @@ HOST_CONFIGURE_ARGS = \
 	--localstatedir=$(HOST_BUILD_PREFIX)/var \
 	--sbindir=$(HOST_BUILD_PREFIX)/bin
 
-ifneq ($(YEAR_2038),y)
-  HOST_CONFIGURE_ARGS += --disable-year2038
-endif
+HOST_CONFIGURE_ARGS += $(if $(filter y,$(YEAR_2038)),,--disable-year2038)
 
 HOST_MAKE_VARS = \
 	CFLAGS="$(HOST_CFLAGS)" \