package/pkg-cargo: allow packages to define download environment
Currently, the cargo infrastructure forcibly sets the package _DL_ENV
variable, instead of appending to it, which prevents packages from
providing their own download environment variables.
We fix that by using an append-assignment.
Note: when introduced, that variable was explicitly not documented, and
is supposed to only be used by packages infrastructures. However, that
variable exists, and it can be (ab)used by br2-external packages (most
probably to ill effects, but heh!). We anyway leave it undocumented,
like _ROOTFS_PRE_CMD_HOOKS.
Signed-off-by: Yann E. MORIN <yann.morin@orange.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Yann E. MORIN