Use standard C compiler by default

Always use the standard compiler as defined by the environment
variable CC. User can set it when a different compiler if required
(e.g. CC=clang make)

demo/allegro5/Makefile

@@ -1,10 +1,6 @@
 # Install
 BIN = demo
 
-# Compiler
-CC = clang
-DCC = gcc
-
 # Flags
 CFLAGS = -std=c89 -pedantic
 
@@ -23,15 +19,6 @@ else
 	endif
 endif
 
-# Modes
-.PHONY: gcc
-gcc: CC = gcc
-gcc: $(BIN)
-
-.PHONY: clang
-clang: CC = clang
-clang: $(BIN)
-
 $(BIN):
 	@mkdir -p bin
 	rm -f bin/$(BIN) $(OBJS)

demo/glfw/Makefile

@@ -1,10 +1,6 @@
 # Install
 BIN = demo
 
-# Compiler
-CC = clang
-DCC = gcc
-
 # Flags
 CFLAGS = -std=c99 -pedantic -O2
 
@@ -23,15 +19,6 @@ else
 	endif
 endif
 
-# Modes
-.PHONY: clang
-clang: CC = clang
-clang: $(BIN)
-
-.PHONY: gcc
-gcc: CC = gcc
-gcc: $(BIN)
-
 $(BIN):
 	@mkdir -p bin
 	rm -f bin/$(BIN) $(OBJS)

demo/sdl/Makefile

@@ -1,10 +1,6 @@
 # Install
 BIN = demo
 
-# Compiler
-CC = clang
-DCC = gcc
-
 # Flags
 CFLAGS = -std=c99 -pedantic -O2
 
@@ -23,15 +19,6 @@ else
 	endif
 endif
 
-# Modes
-.PHONY: clang
-clang: CC = clang
-clang: $(BIN)
-
-.PHONY: gcc
-gcc: CC = gcc
-gcc: $(BIN)
-
 $(BIN):
 	@mkdir -p bin
 	rm -f bin/$(BIN) $(OBJS)

demo/x11/Makefile

@@ -1,25 +1,12 @@
 # Install
 BIN = zahnrad
 
-# Compiler
-CC = clang
-DCC = gcc
-
 # Flags
 CFLAGS = -std=c89 -pedantic -O2
 
 SRC = main.c
 OBJ = $(SRC:.c=.o)
 
-# Modes
-.PHONY: gcc
-gcc: CC = gcc
-gcc: $(BIN)
-
-.PHONY: clang
-clang: CC = clang
-clang: $(BIN)
-
 $(BIN):
 	@mkdir -p bin
 	rm -f bin/$(BIN) $(OBJS)

example/Makefile

@@ -1,6 +1,3 @@
-# Compiler
-CC = clang
-
 # Flags
 CFLAGS = -std=c99 -pedantic -O2