Update Makefiles for C code.

C/Makefile

@@ -20,6 +20,6 @@ example: sources headers build
 	make -C example
 
 clean:
+	rm -rf ./build/*
 	make -C include clean
-	make -C src clean
-	make -C example clean
+	make -C src clean

C/example/Makefile

@@ -1,11 +1,6 @@
 CFLAGS=-O3 -funroll-loops -fmax-errors=1
 
-.PHONY: clean
-
 all: example
 
 example: example.c
-	gcc $< -I../include -L../build/ -lcodata $(CFLAGS) $(FPM_CFLAGS) -o ../build/$@ -Wl,-rpath=.
-
-clean:
-	rm -rf ./build/example*
+	gcc $< -I../include -L../build/ -lcodata $(CFLAGS) $(FPM_CFLAGS) -o ../build/$@ -Wl,-rpath=.

C/src/Makefile

@@ -47,5 +47,4 @@ shared_windows:
 	$(CC) -shared $(FPM_LDFLAGS) -o $(CBUILD_DIR)/$(LIBNAME).dll -Wl,--out-implib=$(CBUILD_DIR)/$(LIBNAME).dll.a,--export-all-symbols,--enable-auto-import,--whole-archive $(CBUILD_DIR)/$(LIBNAME).a -Wl,--no-whole-archive
 
 clean:
-	rm -rf $(C_SRC)
-	rm -rf $(CBUILD_DIR)/*
+	rm -rf $(C_SRC)