Generating Licensing Headers do not work on Ubuntu Linux

[BluThaitanium]

Describe the bug
Running ./hack/add_license_headers.sh returns:

sed: can't read 1i\
    // Copyright 2021 The MLX Contributors\
    //\
    // SPDX-License-Identifier: Apache-2.0\
    : No such file or directory

@ckadner

[BluThaitanium]

From StackOverflow:
Command for sed in Linux
sed -i 's/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g' filename
Command for sed in MacOS
sed -i '' 's/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g' filename

[BluThaitanium]

I tried this on my machine and it works:

hash_comment () {
  echo "$1"
  if ! grep -q "SPDX-License-Identifier" "$1"
  then                                          # Detects OS and uses the correct sed command for each OS
    if [[ "$OSTYPE" == "linux-gnu"* ]]; then          # linux-gnu should work for all linux distributions
      sed -i '1i\
      # Copyright 2021 The MLX Contributors\
      #\
      # SPDX-License-Identifier: Apache-2.0\
      ' "$1"
    elif [[ "$OSTYPE" == "darwin"* ]]; then           # "darwin" is MacOS
      sed -i '' '1i\
      # Copyright 2021 The MLX Contributors\
      #\
      # SPDX-License-Identifier: Apache-2.0\
      ' "$1"
    fi
  fi
}

[ckadner]

Closed by #250