build: bump the com_github_bazelbuild_buildtools version to 0.12.0 (angular#25917)

This is a preliminary fix to make buildifier work with Bazel 0.16.

See angular/angular-bazel-example/issues/173

PR Close angular#25917

Author: IgorMinar

WORKSPACE

@@ -32,13 +32,13 @@ http_archive(
 # This commit matches the version of buildifier in angular/ngcontainer
 # If you change this, also check if it matches the version in the angular/ngcontainer
 # version in /.circleci/config.yml
-BAZEL_BUILDTOOLS_VERSION = "82b21607e00913b16fe1c51bec80232d9d6de31c"
+BAZEL_BUILDTOOLS_VERSION = "49a6c199e3fbf5d94534b2771868677d3f9c6de9"
 
 http_archive(
     name = "com_github_bazelbuild_buildtools",
     url = "https://github.com/bazelbuild/buildtools/archive/%s.zip" % BAZEL_BUILDTOOLS_VERSION,
     strip_prefix = "buildtools-%s" % BAZEL_BUILDTOOLS_VERSION,
-    sha256 = "edb24c2f9c55b10a820ec74db0564415c0cf553fa55e9fc709a6332fb6685eff",
+    sha256 = "edf39af5fc257521e4af4c40829fffe8fba6d0ebff9f4dd69a6f8f1223ae047b",
 )
 
 # Fetching the Bazel source code allows us to compile the Skylark linter