Fix raylib compiling on Linux

src/makefile

@@ -91,7 +91,7 @@ else
 endif
 
 # define all object files required
-OBJS = core.o rlgl.o raymath.o shapes.o text.o textures.o models.o audio.o utils.o camera.o gestures.o stb_vorbis.o
+OBJS = core.o rlgl.o glad.o shapes.o text.o textures.o models.o audio.o utils.o camera.o gestures.o stb_vorbis.o
 
 # typing 'make' will invoke the first target entry in the file,
 # in this case, the 'default' target entry is raylib
@@ -114,9 +114,9 @@ core.o: core.c
 rlgl.o: rlgl.c
 	$(CC) -c rlgl.c $(CFLAGS) $(INCLUDES) -D$(PLATFORM) -D$(GRAPHICS)
 
-# compile raymath module
-raymath.o: raymath.c
-	$(CC) -c raymath.c $(CFLAGS) $(INCLUDES)
+# compile glad module
+raymath.o: glad.c
+	$(CC) -c glad.c $(CFLAGS) $(INCLUDES)
 
 # compile shapes module
 shapes.o: shapes.c