package: pass TARGET_MAKE_ENV at install/clean/uninstall steps

TARGET_MAKE_ENV contains the PATH to the host tools built in
$(HOST_DIR), and not having this directory in the PATH while
installing packages may cause troubles.

The specific example that trigerred the problem is the following
one. libglib2 ./configure tries to find a awk version, either gawk or
mawk. On my limited testing system, only mawk is available, so
normally, libglib2 detects mawk and uses it, and it works perfectly.

However, when host-gawk has been compiled before libglib2 (which
happens for example if you have used the Crosstool-NG backend), gawk
is well detected in $(HOST_DIR)/usr/bin at ./configure time
($(HOST_DIR)/usr/bin is in the PATH at ./configure time, thanks to
TARGET_MAKE_ENV). But at install time, when libglib2 uses gawk, it
doesn't find it anymore because it is not in the PATH.

This also makes things coherent with host installation, in which
$(HOST_MAKE_ENV) was already used.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>