Search for libdevice relative to shared library

[malfet]

If Triton is shipped as shared library inside python package, search for libdevice.10.bc relative to this library installation path: Triton package installation looks as follows

triton/
       _C/libtriton.so
       third_party/cuda/lib/libdevice.10.bc

Test plan:

CXX=g++-9 pip install git+https://github.com/malfet/triton@5a0fe18751bc15c7035916de55e0892e63c3db77#subdirectory=python

And run following:

import torch

def foo(x: torch.Tensor) -> torch.Tensor:
   return torch.sin(x) + torch.cos(x)

if __name__=="__main__":
    x = torch.rand(3, 3, device="cuda")
    x_eager = foo(x)
    x_pt2 = torch.compile(foo)(x)
    print(torch.allclose(x_eager, x_pt2))