toolchain-buildroot: convert to the package infrastructure

This commit converts the toolchain-buildroot logic to the package
infrastructure. The package is fairly simple as it only defines
BUILDROOT_LIBC, and depends on host-gcc-final to get the overall
internal toolchain build logic started.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

toolchain/toolchain-buildroot.mk

@@ -1,9 +0,0 @@
-# Triggerring the build of the host-gcc-final will automaticaly do the
-# build of binutils, uClibc, kernel headers and all the intermediate
-# gcc steps.
-
-include toolchain/helpers.mk
-
-BUILDROOT_LIBC = $(call qstrip,$(BR2_TOOLCHAIN_BUILDROOT_LIBC))
-
-toolchain-buildroot: host-gcc-final

toolchain/toolchain-buildroot/toolchain-buildroot.mk

@@ -0,0 +1,17 @@
+################################################################################
+#
+# toolchain-buildroot
+#
+################################################################################
+
+TOOLCHAIN_BUILDROOT_SOURCE =
+
+BUILDROOT_LIBC = $(call qstrip,$(BR2_TOOLCHAIN_BUILDROOT_LIBC))
+
+# Trigerring the build of the host-gcc-final will automatically do the
+# build of binutils, uClibc, kernel headers and all the intermediate
+# gcc steps.
+
+TOOLCHAIN_BUILDROOT_DEPENDENCIES = host-gcc-final
+
+$(eval $(generic-package))