fix submodules and subprojects download #736

Job	Run time
prepare (mainline)	8m 28s
prepare (buildkit)	8m 16s
prepare (desktop)	10m 7s
validate (./hack/lint)	28s
test (mainline)	3m 53s
validate (./hack/validate-vendor)	17s
test (buildkit)	37s
e2e (mainline, pip-youtube-dl, linux/arm/v7)	1m 27s
test (desktop)	6s
validate (./hack/install-and-test)	38s
e2e (mainline, webpack, linux/arm/v7)	2m 30s
e2e (desktop, pip-youtube-dl, linux/arm/v7)	1m 33s
e2e (desktop, webpack, linux/arm/v7)	2m 32s
e2e (mainline, ejabberd, linux/arm64)	14m 2s
e2e (desktop, tini, linux/arm64, --rm)	47s
e2e (desktop, postgis, linux/arm64, -d --name postgis, postgis, UTC [1] LOG: database system is ...	51s
build (mainline)	34m 7s
build (buildkit)	33m 43s
build (desktop)	33m 27s
	2h 37m 49s

Provide feedback