Create virtual packages for OpenPower toolchain

Create a "toolchain" category, plus "p8-pore-toolchain" and
"ppe42-toolchain" virtual-packages, with the goal of lowering the
coupling between these toolchain and target packages.

Signed-off-by: Klaus Heinrich Kiwi <klaus@linux.vnet.ibm.com>
diff --git a/openpower/package/ppe42-gcc/Config.in b/openpower/package/ppe42-gcc/Config.in
index d66418d..33f5276 100644
--- a/openpower/package/ppe42-gcc/Config.in
+++ b/openpower/package/ppe42-gcc/Config.in
@@ -1,6 +1,12 @@
 config BR2_PACKAGE_HOST_PPE42_GCC
         bool "ppe42-gcc"
         default y if (BR2_OPENPOWER_PLATFORM && BR2_OPENPOWER_POWER9)
+        select BR2_PACKAGE_HAS_PPE42_TOOLCHAIN
         select BR2_CPP
         help
             Project to build the PPE42 gcc
+
+if BR2_PACKAGE_HOST_PPE42_GCC
+config BR2_PACKAGE_PROVIDES_PPE42_TOOLCHAIN
+        default "ppe42-gcc"
+endif