Remove more sha1-generation code

tools/BUILD.bazel

@@ -1,4 +1,3 @@
 exports_files([
-    "sha1",
     "sha256",
 ])

tools/hashes.bzl

@@ -2,14 +2,6 @@ def _impl(ctx):
     in_file = ctx.file.src
 
     basename = ctx.attr.src.label.name
-    out_sha1 = ctx.actions.declare_file("%s.sha1" % basename)
-    ctx.actions.run(
-        executable = ctx.executable._cmd_sha1,
-        outputs = [out_sha1],
-        inputs = [in_file],
-        arguments = [in_file.path, out_sha1.path],
-    )
-
     out_sha256 = ctx.actions.declare_file("%s.sha256" % basename)
     ctx.actions.run(
         executable = ctx.executable._cmd_sha256,
@@ -19,25 +11,18 @@ def _impl(ctx):
     )
 
     return DefaultInfo(
-        files = depset([out_sha1, out_sha256]),
+        files = depset([out_sha256]),
     )
 
 def _get_outputs(src):
     return {
-        "sha1": src.name + ".sha1",
         "sha256": src.name + ".sha256",
     }
 
 hashes = rule(
     implementation = _impl,
     attrs = {
         "src": attr.label(mandatory = True, allow_single_file = True),
-        "_cmd_sha1": attr.label(
-            default = Label("//tools:sha1"),
-            allow_single_file = True,
-            executable = True,
-            cfg = "host",
-        ),
         "_cmd_sha256": attr.label(
             default = Label("//tools:sha256"),
             allow_single_file = True,