Remove uneeded PTX code generation from libfaiss builds (#3083)

Summary:
The CMake CUDA Architecture value of `60` means to generate both PTX and SASS for that arch. We only need SASS for the architectures we support, and one PTX version for future hardware versions.

So now we build on SASS for everything ( `60-real` ) and use 80 as the baseline for newer archs likes 90

By removing this unneeded PTX code we can reduce the libfaiss.a binary to 305MB from the current 484MB.

Pull Request resolved: https://github.com/facebookresearch/faiss/pull/3083

Reviewed By: wickedfoo

Differential Revision: D49901896

Pulled By: algoriddle

fbshipit-source-id: 15e98f81e191a565319cf855debad33b24ebf10b

.circleci/config.yml

@@ -350,7 +350,7 @@ workflows:
           exec: linux-x86_64-gpu
           label: main
           cuda: "11.4"
-          cuda_archs: "60;61;70;72;75;80;86"
+          cuda_archs: "60-real;61-real;62-real;70-real;72-real;75-real;80;86-real"
           compiler_version: "11.2"
           filters:
             tags:
@@ -363,7 +363,7 @@ workflows:
           label: main
           raft: "ON"
           cuda: "11.4"
-          cuda_archs: "60;61;70;72;75;80;86"
+          cuda_archs: "60-real;61-real;62-real;70-real;72-real;75-real;80;86-real"
           compiler_version: "11.2"
           filters:
             tags:
@@ -415,7 +415,7 @@ workflows:
           name: Linux x86_64 GPU nightlies (CUDA 11.4)
           exec: linux-x86_64-gpu
           cuda: "11.4"
-          cuda_archs: "60;61;70;72;75;80;86"
+          cuda_archs: "60-real;61-real;62-real;70-real;72-real;75-real;80;86-real"
           compiler_version: "11.2"
           label: nightly
       - build_conda:
@@ -423,7 +423,7 @@ workflows:
           exec: linux-x86_64-gpu
           raft: "ON"
           cuda: "11.4"
-          cuda_archs: "60;61;70;72;75;80;86"
+          cuda_archs: "60-real;61-real;62-real;70-real;72-real;75-real;80;86-real"
           compiler_version: "11.2"
           label: nightly
       - build_conda: