How to install a package from git into a specific directory using pip -t

I have downloaded all of my requirements in AWS Linux + EFS using

pip3 install -t /mnt/efs/fs1/ml/ -r /mnt/efs/fs1/ml/requirements.txt

They get downloaded without an issue and I'm able to call them too. Now I want to install detectron2 but it has to be done separately as it requires torch already in the system.

I install it with:

pip3 install -t /mnt/efs/fs1/ml/ 'git+https://github.com/facebookresearch/detectron2.git'

Even if I have installed torch in above requirements, and able to import it too. I also installed it in the global path too (without -t) but still I'm getting the error:

pip3 install 'git+https://github.com/facebookresearch/detectron2.git'
Defaulting to user installation because normal site-packages is not writeable
Collecting git+https://github.com/facebookresearch/detectron2.git
  Cloning https://github.com/facebookresearch/detectron2.git to /tmp/pip-req-build-bcthhh9q
    ERROR: Command errored out with exit status 1:
     command: /usr/bin/python3 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-req-build-bcthhh9q/setup.py'"'"'; __file__='"'"'/tmp/pip-req-build-bcthhh9q/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-nmaxo6d1
         cwd: /tmp/pip-req-build-bcthhh9q/
    Complete output (5 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-req-build-bcthhh9q/setup.py", line 10, in <module>
        import torch
    ModuleNotFoundError: No module named 'torch'
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

What is the problem here? The below command runs perfectly in my system when I don't install requirements.txt with -t flag.