Don't consider a workspace directory a marker of being in a workspace
Don't consider a workspace directory a marker of being in a workspace

Jenkins workers tend to place all of their Jenkins workspaces in a
directory named `workspace`. On a case-insensitive filesystem,
Bazel would consider anything run by Jenkins as being in a Bazel
workspace, because of that `workspace` directory being in the
filesystem hierarchy of the cwd.

Avoid this by only looking for _files_ named `workspace` when
determining if a directory is potentially a Bazel workspace.

Closes #10947.

PiperOrigin-RevId: 304553522

ulfjack/bazel,cushon/bazel,akira-baruah/bazel,werkt/bazel,katre/bazel,ButterflyNetwork/bazel,meteorcloudy/bazel,dslomov/bazel-windows,twitter-forks/bazel,cushon/bazel,akira-baruah/bazel,davidzchen/bazel,davidzchen/bazel,akira-baruah/bazel,davidzchen/bazel,ButterflyNetwork/bazel,safarmer/bazel,perezd/bazel,werkt/bazel,katre/bazel,perezd/bazel,ButterflyNetwork/bazel,akira-baruah/bazel,davidzchen/bazel,akira-baruah/bazel,dslomov/bazel,meteorcloudy/bazel,davidzchen/bazel,dslomov/bazel-windows,werkt/bazel,twitter-forks/bazel,ulfjack/bazel,dslomov/bazel-windows,perezd/bazel,meteorcloudy/bazel,bazelbuild/bazel,twitter-forks/bazel,safarmer/bazel,twitter-forks/bazel,safarmer/bazel,katre/bazel,perezd/bazel,ulfjack/bazel,safarmer/bazel,bazelbuild/bazel,werkt/bazel,dslomov/bazel-windows,ButterflyNetwork/bazel,akira-baruah/bazel,twitter-forks/bazel,ulfjack/bazel,dslomov/bazel-windows,ulfjack/bazel,dslomov/bazel,katre/bazel,ButterflyNetwork/bazel,ulfjack/bazel,meteorcloudy/bazel,bazelbuild/bazel,meteorcloudy/bazel,ulfjack/bazel,bazelbuild/bazel,davidzchen/bazel,dslomov/bazel-windows,dslomov/bazel,ButterflyNetwork/bazel,meteorcloudy/bazel,safarmer/bazel,perezd/bazel,cushon/bazel,perezd/bazel,bazelbuild/bazel,cushon/bazel,meteorcloudy/bazel,cushon/bazel,twitter-forks/bazel,katre/bazel,twitter-forks/bazel,bazelbuild/bazel,katre/bazel,dslomov/bazel,safarmer/bazel,davidzchen/bazel,dslomov/bazel,dslomov/bazel,dslomov/bazel,werkt/bazel,perezd/bazel,cushon/bazel,werkt/bazel