if CGO is enabled, make sure to use C.getenv instead of os.Getenv to
read environment variables. It is required since rootless libpod
joins the user namespace through Cgo.
The variables set via C.setenv are not visible through os.Getenv, as
the latter uses sync.Once to read the variables once.
Requires: https://github.com/containers/libpod/pull/4911
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
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