package/pkg-generic: handle host-lzip as an extract dependency

This moves the host-lzip dependency handling from
DEPENDENCY_HOST_PREREQ to an extract dependency.

To achieve that, check-host-lzip.mk fills in the
BR2_LZIP_HOST_DEPENDENCY with host-lzip if building a host-lzip is
needed. The name BR2_LZIP_HOST_DEPENDENCY has been chosen because it
matches the name BR2_CMAKE_HOST_DEPENDENCY already used in
check-host-cmake.mk.

The BR2_LZIP_HOST_DEPENDENCY is added to all packages, except:

 - host-lzip, because we would otherwise depend on ourself.

 - host-tar, because lzip itself is delivered as a tarball, so we need
   to have host-lzip depend on host-tar, and not host-tar depend on
   host-lzip

 - host-skeleton, because we need to have host-lzip depend on
   host-skeleton, and not the opposite.

We also mutually exclude host-lzip and host-xz from dependending on
each other, to avoid a circular dependency.

In addition, we modify lzip.mk to explicitly build host-lzip without
ccache. We generally took the approach of building host-ccache *after*
all the extractors have been built.

[Peter: fix s/host-tar/host-lzip/ typo, fix s/xz/lzip/ typo]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

support/dependencies/check-host-lzip.mk

@@ -1,5 +1,5 @@
 ifeq (,$(call suitable-host-package,lzip,$(LZCAT)))
-DEPENDENCIES_HOST_PREREQ += host-lzip
+BR2_LZIP_HOST_DEPENDENCY = host-lzip
 EXTRACTOR_DEPENDENCY_PRECHECKED_EXTENSIONS += .lz
 LZCAT = $(HOST_DIR)/bin/lzip -d -c
 endif