CMAKE_BUILD_TYPE set to Release by default: improved
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3d2b030..fe41183 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.0)
 
-if(NOT CMAKE_BUILD_TYPE)
-    set(CMAKE_BUILD_TYPE Release)
+if(NOT (CMAKE_BUILD_TYPE OR CMAKE_CONFIGURATION_TYPES OR DEFINED ENV{CFLAGS} OR DEFINED ENV{CXXFLAGS}))
+    set(CMAKE_BUILD_TYPE Release CACHE STRING "Choose the type of build, options are: None Debug Release RelWithDebInfo")
 endif()
 
 project(FLAC VERSION 1.3.2) # HOMEPAGE_URL "https://www.xiph.org/flac/")