buildroot

core-dependencies: remove unneeded HOSTCC

dependencies.sh uses HOSTCC_NOCCACHE directly, and this variable is
exported from the top-level Makefile, so there is no need to pass
HOSTCC to it. HOSTCC is not used at all in dependencies.sh.

Thus, we also no longer need to apply the HOSTCC override for
core-dependencies. The core-depencies rule doesn't use HOSTCC or
HOSTCXX.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>