docker: cleanup and split off ccache into separate function

docker_build_wrap.sh

@@ -7,7 +7,7 @@
 #   BUILD_DEPENDS  (may be used by config.sh, can be empty)
 set -e
 
-if [ $USE_CCACHE == 1 ]; then
+function activate_ccache {
     # Link up the correct location for ccache
     ln -s /parent-home/.ccache $HOME/.ccache
 
@@ -17,16 +17,20 @@ if [ $USE_CCACHE == 1 ]; then
     # Create fake compilers and prepend them to the PATH
     # Note that yum is supposed to create these for us,
     # but I had trouble finding them
-  CCACHE_DIR=/usr/lib/ccache/compilers
-  mkdir -p $CCACHE_DIR
+    local ccache_dir=/usr/lib/ccache/compilers
+    mkdir -p $ccache_dir
     ln -s /usr/bin/ccache $CCACHE_DIR/gcc
     ln -s /usr/bin/ccache $CCACHE_DIR/g++
     ln -s /usr/bin/ccache $CCACHE_DIR/cc
     ln -s /usr/bin/ccache $CCACHE_DIR/c++
     export PATH=$CCACHE_DIR:$PATH
 
-  # Prove to the developer that the correct gcc is used
+    # Prove to the developer that ccache is activated
     which gcc
+}
+
+if [ $USE_CCACHE == 1 ]; then
+    activate_ccache
 fi
 
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