Add an important warning message

Build-the-library-for-GNU-Linux.md

@@ -40,6 +40,8 @@ First of all, you need to download raylib repository from Github; after you can
     make PLATFORM=PLATFORM_DESKTOP SHARED=YES # To make the dynamic shared version.
     make PLATFORM=PLATFORM_WEB # To make web version.
 
+**Warning:** if you want to compile a different type of library (static, ...), you must type `make clean` before the compiling.
+
 _NOTE:_ By default raylib is compiled for OpenGL 3.3 Core graphics API backend; to compile for OpenGL 1.1 graphics API just add `GRAPHICS=GRAPHICS_API_OPENGL_11` to the make command.
 
 If you want, you can install the library in the standard directories, or remove it: