Update min bazel version to 0.6.0
Summary: 0.6.0 introduces a new file (dummy_toolchain.bzl) in bazel_tools and our build fails if this file isn't present.
Reviewers: shahms, zarko
Subscribers: #core_team
@@ -4,7 +4,7 @@ load("//:version.bzl", "check_version")
# Check that the user has a version between our minimum supported version of
# Bazel and our maximum supported version of Bazel.
-check_version("0.4.5", "0.6.0")
+check_version("0.6.0", "0.6.0")
load("//tools/cpp:clang_configure.bzl", "clang_configure")
