Update bazel to fix some Incompatible Target Skipping bugs

This is the same version as 4.0.0rc2 except with 2 cherry-picks:
a3c94ec2ed Fix builds for filegroup targets with incompatible dependencies
b3c9d7381c Fix a couple of bugs with Incompatible Target Skipping

The patch for the filegroup fix has already merged on master:
https://github.com/bazelbuild/bazel/pull/12601

The other patch is still under review:
https://github.com/bazelbuild/bazel/pull/12560

This should enable us to convert the code base to use platforms.

Change-Id: I35f078c2576f5268d5e3fb33e9bd86732529f744
diff --git a/tools/bazel b/tools/bazel
index 36e88ae..21bb619 100755
--- a/tools/bazel
+++ b/tools/bazel
@@ -24,7 +24,7 @@
   exec "${BAZEL_OVERRIDE}" "$@"
 fi
 
-readonly VERSION="4.0.0rc2-202011211956+37a429ad12"
+readonly VERSION="4.0.0rc2-202012022031+a3c94ec2ed"
 
 readonly DOWNLOAD_DIR="${HOME}/.cache/bazel"
 # Directory to unpack bazel into.  This must change whenever bazel changes.