Fix build system

Fixed 'commands commence before first target' error caused by TAB
characters before $(warning ...) function calls.
- Lines starting with TAB are treated as recipe commands
- Recipe commands must be inside a target rule
- Function calls like $(warning ...) should NOT start with TAB

Author: jserv

mk/toolchain.mk

@@ -22,10 +22,10 @@ ifneq ($(shell $(CC) --version | head -n 1 | grep emcc),)
                 $(warning $(SDL_MUSIC_CANNOT_PLAY_WARNING))
             endif
         else
-	    $(warning $(SDL_MUSIC_CANNOT_PLAY_WARNING))
+        $(warning $(SDL_MUSIC_CANNOT_PLAY_WARNING))
         endif
     else
-	$(warning $(SDL_MUSIC_CANNOT_PLAY_WARNING))
+        $(warning $(SDL_MUSIC_CANNOT_PLAY_WARNING))
     endif
 
     # see commit 165c1a3 of emscripten