add flex to apt install list
MODIFY
README.md
README.md
@@ -137,7 +137,7 @@ afl++ has many build options.
The easiest is to build and install everything:
```shell
-$ sudo apt install build-essential libtool-bin python3 automake bison libglib2.0-dev libpixman-1-dev clang python-setuptools llvm
+$ sudo apt install build-essential libtool-bin python3 automake flex bison libglib2.0-dev libpixman-1-dev clang python-setuptools llvm
$ make distrib
$ sudo make install
```

add flex to apt install list