ci: build tftf with -j=ncores

Tftf can build with lots of cores just fine but they are never given to
the make command. Allow this on local runs.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I982b2bc9d2e6519042c665e01b9b3d709b25a03f
diff --git a/script/build_package.sh b/script/build_package.sh
index 97230b6..46ef0b5 100755
--- a/script/build_package.sh
+++ b/script/build_package.sh
@@ -622,11 +622,11 @@
 	cat <<EOF | log_separator >/dev/null
 
 Build command line:
-	make $(cat "$config_file" | tr '\n' ' ') DEBUG=$DEBUG V=1 $build_targets
+	make $make_j_opts $(cat "$config_file" | tr '\n' ' ') DEBUG=$DEBUG V=1 $build_targets
 
 EOF
 
-	make $(cat "$config_file") DEBUG="$DEBUG" V=1 \
+	make $make_j_opts $(cat "$config_file") DEBUG="$DEBUG" V=1 \
 		$build_targets &>>"$build_log" || fail_build
 	)
 }