pkg-rebar: HOST_CC -> HOSTCC

Fix HOSTCC typo that would cause host-rebar builds to fail.

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/pkg-rebar.mk

@@ -209,7 +209,7 @@ $(2)_CONF_ENV += $$(REBAR_HOST_DEPS_ENV)
 ifndef $(2)_BUILD_CMDS
 define $(2)_BUILD_CMDS
 	(cd $$(@D); \
-		CC="$$(HOST_CC)" \
+		CC="$$(HOSTCC)" \
 		CFLAGS="$$(HOST_CFLAGS)" \
 		LDFLAGS="$$(HOST_LDFLAGS)" \
 		$$(REBAR_HOST_DEPS_ENV) \