configs: Add common toolchain configuration file

This commit introduces the common toolchain configuration file,
common.config, that specifies the crosstool-ng toolchain configurations
that are common to all toolchain variants.

The configurations in common.config are applied before the
configurations in each toolchain configuration file.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

.github/workflows/ci.yml

@@ -624,8 +624,9 @@ jobs:
         pushd ${WORKSPACE}/build
 
         # Load default target configurations
-        cp ${GITHUB_WORKSPACE}/configs/${{ matrix.target }}.config \
-           .config
+        cat ${GITHUB_WORKSPACE}/configs/common.config \
+            ${GITHUB_WORKSPACE}/configs/${{ matrix.target }}.config \
+            > .config
 
         # Set version information
         cat <<EOF >> .config

configs/common.config

@@ -0,0 +1 @@
+# Common crosstool-ng configurations for all toolchain variants