Fix LOG_DIR directory creation error.
Add support for automatic creation of BUILD_DIR directory.
diff --git a/Makefile b/Makefile
index fc7b117..a4aa19f 100644
--- a/Makefile
+++ b/Makefile
@@ -74,6 +74,11 @@
ifneq ($(BUILD_DIR),)
saved-output := $(BUILD_DIR)
+
+# Attempt to create a output directory.
+$(shell [ -d ${BUILD_DIR} ] || mkdir -p ${BUILD_DIR})
+
+# Verify if it was successful.
BUILD_DIR := $(shell cd $(BUILD_DIR) && /bin/pwd)
$(if $(BUILD_DIR),,$(error output directory "$(saved-output)" does not exist))
endif # ifneq ($(BUILD_DIR),)