Currently, we set TOOLCHAIN_INSTALL_STAGING three times: once
(conditionally) in toolchain.mk, and once each (unconditionally) in
pkg-cmake.mk and pkg-meson.mk.
This is a little bit messy... Set it just once, unconditionally, in
toolchain.mk where it belongs.
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>