build: do not depend on $(STAGING_DIR)/.prepared when in SDK

The dependency can't be satisfied when building using the SDK, breaking
package builds. As the staging and bin dirs are distributed with the SDK
archive, ignoring the dependency is fine when SDK is set.

Fixes: fbb924abff ("build: add $(STAGING_DIR) and $(BIN_DIR) ...")
Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
(cherry picked from commit 2b46cbef81)

package/Makefile

@@ -59,6 +59,7 @@ $(curdir)/merge-index: $(curdir)/merge
 	(cd $(PACKAGE_DIR_ALL) && $(SCRIPT_DIR)/ipkg-make-index.sh . 2>&1 > Packages; )
 
 ifndef SDK
+  $(curdir)//compile = $(STAGING_DIR)/.prepared $(BIN_DIR)
   $(curdir)/compile: $(curdir)/system/opkg/host/compile
 endif
 
@@ -117,8 +118,6 @@ endif
 
 $(curdir)/flags-install:= -j1
 
-$(curdir)//compile = $(STAGING_DIR)/.prepared $(BIN_DIR)
-
 $(eval $(call stampfile,$(curdir),package,prereq,.config))
 $(eval $(call stampfile,$(curdir),package,cleanup,$(TMP_DIR)/.build))
 $(eval $(call stampfile,$(curdir),package,compile,$(TMP_DIR)/.build))