Deduplicate expand_location targets in rust-project.json crate creation

There's a bug in bazel where the server crashes if it encounters
duplicate entries in expand_location's targets field.
See bazelbuild/bazel#16664

rust/private/rust_analyzer.bzl

@@ -182,9 +182,13 @@ def _create_single_crate(ctx, info):
             "include_dirs": [crate_root, _EXEC_ROOT_TEMPLATE + out_dir_path],
         }
 
+    # We deduplicate the entries from each of the additional targets to work around
+    # https://github.com/bazelbuild/bazel/issues/16664
+    #
     # TODO: The only imagined use case is an env var holding a filename in the workspace passed to a
     # macro like include_bytes!. Other use cases might exist that require more complex logic.
-    expand_targets = getattr(ctx.rule.attr, "data", []) + getattr(ctx.rule.attr, "compile_data", [])
+    expand_targets = _deduplicate(_concat([getattr(ctx.rule.attr, attr, []) for attr in ["data", "compile_data"]]))
+
     crate["env"].update({k: ctx.expand_location(v, expand_targets) for k, v in info.env.items()})
 
     # Omit when a crate appears to depend on itself (e.g. foo_test crates).
@@ -204,6 +208,12 @@ def _create_single_crate(ctx, info):
         crate["proc_macro_dylib_path"] = _EXEC_ROOT_TEMPLATE + info.proc_macro_dylib_path
     return crate
 
+def _deduplicate(xs):
+    return {x: True for x in xs}.keys()
+
+def _concat(xss):
+    return [x for xs in xss for x in xs]
+
 def _rust_analyzer_toolchain_impl(ctx):
     toolchain = platform_common.ToolchainInfo(
         rustc_srcs = ctx.attr.rustc_srcs,