Upgrading `pkg` causes a pause on input prompting.

[Yasutaka ATARASHI]

During upgrading pkg, it occurs pause on prompting:

The package management tool is not yet installed on your system.
Do you want to fetch and install it now? [y/N]:

because pkg is deleted tentatively.
Maybe, pkg-static is used for pkg info -E "*".
pkg-static itself is installed as pkg/ports so check pkg -N and skip invocation if necesary

[Yasutaka ATARASHI]

/usr/ports/ports-mgmt/pkg/Makefile has the following configuration:

# Use the internal pkg instead, generally, unless this is a cross-build,
# in which case that won't work. Hope for the best then.
.if !defined(CROSS_TOOLCHAIN)
PKG_BIN=        ${WRKSRC}/src/pkg-static
.endif

So, this configuration should be passed to wrappers.