add "prepare-ccache" as a tool for travis

also bullet-proof setting up ccache against parallelization race conditions

bin/kaleidoscope-builder

@@ -67,7 +67,6 @@ enable_ccache () {
     if [ -z "${CCACHE_NOT_SUPPORTED}" ] && [ "$(command -v ccache)" ]; then
       if ! [ -d "$CCACHE_WRAPPER_PATH" ]; then
          mkdir -p "$CCACHE_WRAPPER_PATH"
-      fi
 
           if ! [ -h "${CCACHE_WRAPPER_PATH}/${COMPILER_PREFIX}${C_COMPILER_BASENAME}" ]; then
              ln -s "$(command -v ccache)" "${CCACHE_WRAPPER_PATH}/${COMPILER_PREFIX}${C_COMPILER_BASENAME}"
@@ -92,6 +91,7 @@ enable_ccache () {
           if ! [ -h "${CCACHE_WRAPPER_PATH}/${COMPILER_PREFIX}size" ]; then
              ln -s "${AVR_SIZE}" "${CCACHE_WRAPPER_PATH}/${COMPILER_PREFIX}size"
           fi
+      fi
 
       export CCACHE_PATH=${COMPILER_PATH}/
       CCACHE_ENABLE="-prefs compiler.path=${CCACHE_WRAPPER_PATH}/"
@@ -345,6 +345,12 @@ build () {
     size "$@"
 }
 
+
+prepare_ccache () {
+    build_paths
+    enable_ccache
+}
+
 compile () {
     find_sketch
     build_version