I have an error while making my makefile in linux. Here's my code: 

```make
CC = gcc
CFLAGS = -Wall -m32 -g -fno-stack-protector -z execstack -O0
SHELL_SOURCES = Shell.c

SHELL = Shell

.PHONY: all target1 clean

all: target1 

target1: $(SHELL)

$(SHELL): $(SHELL_SOURCES)
    $(CC) $(CFLAGS) $^ -o $@

clean:
rm -rf $(SHELL)

```

The error I get is: 

```
gcc -Wall -m32 -g -fno-stack-protector -z execstack -O0 Shell.c -o Shell
make: Shell: Command not found
Makefile:16: recipe for target 'Shell' failed
make: *** [Shell] Error 127

```