fix formatting CIRCLE_TAG when building docs (#67026) (#69876)

Summary:
Similar to pytorch/text#1416
malfet, brianjo

The previous code failed when tags changed from `v0.9.0` to `v0.10.0`. I tested this offline, it would be nice to somehow be actually tag the repo and see that this adds the correct documentation directory to the pytorch/pytorch.github.io repo.

Pull Request resolved: #67026

Reviewed By: saketh-are

Differential Revision: D31843381

Pulled By: malfet

fbshipit-source-id: 21526ad9ed4c1751c2d7f6d621da305f166a7f55

Co-authored-by: mattip <matti.picus@gmail.com>

.circleci/verbatim-sources/job-specs/job-specs-custom.yml

@@ -43,7 +43,8 @@
           set -ex
           export COMMIT_DOCKER_IMAGE=${DOCKER_IMAGE}:build-${DOCKER_TAG}-${CIRCLE_SHA1}
           echo "DOCKER_IMAGE: "${COMMIT_DOCKER_IMAGE}
-          tag=${CIRCLE_TAG:1:5}
+          # turn v1.12.0rc3 into 1.12.0
+          tag=$(echo $CIRCLE_TAG | sed -e 's/v*\([0-9.]*\).*/\1/')
           target=${tag:-master}
           echo "building for ${target}"
           time docker pull ${COMMIT_DOCKER_IMAGE} >/dev/null
@@ -88,6 +89,8 @@
           set -ex
           export COMMIT_DOCKER_IMAGE=${DOCKER_IMAGE}:build-${DOCKER_TAG}-${CIRCLE_SHA1}
           echo "DOCKER_IMAGE: "${COMMIT_DOCKER_IMAGE}
+          # turn v1.12.0rc3 into 1.12.0
+          tag=$(echo $CIRCLE_TAG | sed -e 's/v*\([0-9.]*\).*/\1/')
           tag=${CIRCLE_TAG:1:5}
           target=${tag:-master}
           echo "building for ${target}"