inject.sh: always re-build nvmutil

it's not a lot of code, and takes less than a second.

the previous change uses x instead of ?, but this would
cause an error if the nvmutil was already built, because
the makefile might cause a build to be skipped.

therefore, force a re-build to mitigate the error.

Signed-off-by: Leah Rowe <leah@libreboot.org>

include/inject.sh

@@ -132,7 +132,8 @@ modify_mac()
 	[ -n "$CONFIG_GBE_BIN_PATH" ] || return 1
 
 	x_ cp "${CONFIG_GBE_BIN_PATH##*../}" tmp/gbe
-	[ "$new_mac" != "restore" ] && x_ make -C util/nvmutil && \
+	[ "$new_mac" != "restore" ] && x_ make -C util/nvmutil clean && \
+	    x_ make -C util/nvmutil && \
 	    x_ "$nvm" tmp/gbe setmac "$new_mac"
 
 	fe_ newmac "$tmpromdir" -maxdepth 1 -type f -name "*.rom"