Added development option, through an error message to user who want to build GLM

CMakeLists.txt

@@ -19,5 +19,8 @@ add_subdirectory(test)
 add_subdirectory(bench)
 add_subdirectory(doc)
 
-
+option(GLM_DEVELOPMENT_MODE "GLM development" OFF)
+if(NOT GLM_DEVELOPMENT_MODE)
+	message(FATAL_ERROR "GLM is a header only library, no need to build it")
+endif()