package/sed: make HOST_SED_BINARY a simply expanded variable (:=)

HOST_SED_BINARY is used 2 times during startup, and is relatively
expensive to run, so make it a simple expanded variable (:=) rather
than a recursively expanded one (=).

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/sed/sed.mk

@@ -17,7 +17,7 @@ endif
 #HOST_SED_DIR:=$(STAGING_DIR)
 HOST_SED_DIR:=$(TOOLCHAIN_DIR)
 SED:=$(HOST_SED_DIR)/bin/sed -i -e
-HOST_SED_BINARY=$(shell package/sed/sedcheck.sh)
+HOST_SED_BINARY:=$(shell package/sed/sedcheck.sh)
 HOST_SED_IF_ANY=$(shell toolchain/dependencies/check-host-sed.sh)
 
 $(DL_DIR)/$(SED_SOURCE):