host-ccache: turn into a proper dependency

This patch moves the host-ccache build target from BASE_TARGETS in Makefile
to an actual host prerequisite in support/dependencies. This causes
host-ccache to be built as part of the dependencies, before any real package
is built.
Since the dependencies are built without ccache anyway, there is no need to
set HOST_CCACHE_CONF_ENV anymore.

Suggested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Acked-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Makefile

@@ -222,10 +222,6 @@ GNU_HOST_NAME:=$(shell support/gnuconfig/config.guess)
 #
 ################################################################################
 
-ifeq ($(BR2_CCACHE),y)
-BASE_TARGETS += host-ccache
-endif
-
 ifeq ($(BR2_TOOLCHAIN_BUILDROOT),y)
 BASE_TARGETS += toolchain-buildroot
 else ifeq ($(BR2_TOOLCHAIN_EXTERNAL),y)

package/ccache/ccache.mk

@@ -10,12 +10,6 @@ CCACHE_SOURCE  = ccache-$(CCACHE_VERSION).tar.bz2
 CCACHE_LICENSE = GPLv3+, others
 CCACHE_LICENSE_FILES = LICENSE.txt GPL-3.0.txt
 
-# When ccache is being built for the host, ccache is not yet
-# available, so we have to use the special C compiler without the
-# cache.
-HOST_CCACHE_CONF_ENV = \
-	CC="$(HOSTCC_NOCCACHE)"
-
 # Force ccache to use its internal zlib. The problem is that without
 # this, ccache would link against the zlib of the build system, but we
 # might build and install a different version of zlib in $(O)/host

support/dependencies/dependencies.mk

@@ -20,6 +20,10 @@ ifeq ($(BR2_STRIP_sstrip),y)
 DEPENDENCIES_HOST_PREREQ+=host-sstrip
 endif
 
+ifeq ($(BR2_CCACHE),y)
+DEPENDENCIES_HOST_PREREQ += host-ccache
+endif
+
 core-dependencies:
 	@HOSTCC="$(firstword $(HOSTCC))" MAKE="$(MAKE)" \
 		DL_TOOLS="$(sort $(DL_TOOLS_DEPENDENCIES))" \