build_target_util: Rename to build_target_lib.

Nitty name change. The module contains a class and is in lib, so
should be a _lib, not a _util.

BUG=chromium:1060351
TEST=run_tests

Change-Id: I539dc8e5288e71cc9408bc68861f20579ac70937
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2095746
Commit-Queue: Alex Klein <saklein@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/api/controller/artifacts.py b/api/controller/artifacts.py
index c7f3793..31d75d0 100644
--- a/api/controller/artifacts.py
+++ b/api/controller/artifacts.py
@@ -16,7 +16,7 @@
 from chromite.api.controller import controller_util
 from chromite.api.gen.chromite.api import toolchain_pb2
 from chromite.cbuildbot import commands
-from chromite.lib import build_target_util
+from chromite.lib import build_target_lib
 from chromite.lib import chroot_lib
 from chromite.lib import constants
 from chromite.lib import cros_build_lib
@@ -466,7 +466,7 @@
   cache_dir = input_proto.chroot.cache_dir
 
   # Build out the argument instances.
-  build_target = build_target_util.BuildTarget(build_target_name)
+  build_target = build_target_lib.BuildTarget(build_target_name)
   chroot = chroot_lib.Chroot(path=chroot_path, cache_dir=cache_dir)
   # Sysroot.path needs to be the fully qualified path, including the chroot.
   full_sysroot_path = os.path.join(chroot.path, sysroot_path.lstrip(os.sep))
@@ -540,7 +540,7 @@
   """
 
   # Required args.
-  build_target = build_target_util.BuildTarget(input_proto.build_target.name)
+  build_target = build_target_lib.BuildTarget(input_proto.build_target.name)
   chrome_root = input_proto.chroot.chrome_dir
   if not chrome_root:
     cros_build_lib.Die('chrome_root is not included in chroot')