Update dependencies, fix a few incompatible issues (#166)

Tested:
  bazel-0.20.0rc4 test //... --all_incompatible_changes --incompatible_disable_deprecated_attr_params=false --incompatible_depset_is_not_iterable=false --incompatible_depset_union=false --incompatible_new_actions_api=false

WORKSPACE

@@ -17,6 +17,13 @@ local_repository(
     path = "docs",
 )
 
+http_archive(
+    name = "bazel_skylib",
+    sha256 = "eb5c57e4c12e68c0c20bc774bfbc60a568e800d025557bc4ea022c6479acc867",
+    strip_prefix = "bazel-skylib-0.6.0",
+    url = "https://github.com/bazelbuild/bazel-skylib/archive/0.6.0.tar.gz",
+)
+
 # TODO: Move this to examples/WORKSPACE when recursive repositories are enabled.
 load("//rust:repositories.bzl", "rust_repositories")
 
@@ -36,9 +43,9 @@ rust_proto_repositories()
 # Used for documenting Rust rules.
 http_archive(
     name = "io_bazel_rules_sass",
-    sha256 = "76ae498b9a96fa029f026f8358ed44b93c934dde4691a798cb3a4137c307b7dc",
-    strip_prefix = "rules_sass-1.15.1",
-    url = "https://github.com/bazelbuild/rules_sass/archive/1.15.1.zip",
+    sha256 = "894d7928df8da85e263d743c8434d4c10ab0a3f0708fed0d53394e688e3faf70",
+    strip_prefix = "rules_sass-8ccf4f1c351928b55d5dddf3672e3667f6978d60",
+    url = "https://github.com/bazelbuild/rules_sass/archive/8ccf4f1c351928b55d5dddf3672e3667f6978d60.zip",
 )
 
 load("@io_bazel_rules_sass//:package.bzl", "rules_sass_dependencies")
@@ -69,13 +76,6 @@ http_archive(
     ],
 )
 
-http_archive(
-    name = "bazel_skylib",
-    sha256 = "b5f6abe419da897b7901f90cbab08af958b97a8f3575b0d3dd062ac7ce78541f",
-    strip_prefix = "bazel-skylib-0.5.0",
-    url = "https://github.com/bazelbuild/bazel-skylib/archive/0.5.0.tar.gz",
-)
-
 load(":workspace.bzl", "bazel_version")
 
 bazel_version(name = "bazel_version")

rust/private/rustc.bzl

@@ -94,7 +94,7 @@ def collect_deps(deps, toolchain):
     """
 
     # TODO: Fix depset union (https://docs.bazel.build/versions/master/skylark/depsets.html)
-    direct_crates = depset()
+    direct_crates = []
     transitive_crates = depset()
     transitive_dylibs = depset(order = "topological")  # dylib link flag ordering matters.
     transitive_staticlibs = depset()
@@ -116,13 +116,15 @@ def collect_deps(deps, toolchain):
             fail("rust targets can only depend on rust_library, rust_*_library or cc_library targets." + str(dep), "deps")
 
     crate_list = transitive_crates.to_list()
-    transitive_libs = depset([c.output for c in crate_list]) + transitive_staticlibs + transitive_dylibs
+    transitive_libs = depset(
+        [c.output for c in crate_list],
+        transitive = [transitive_staticlibs, transitive_dylibs],
+    )
 
-    # TODO: Avoid depset flattening.
-    indirect_crates = depset([crate for crate in crate_list if crate not in direct_crates.to_list()])
+    indirect_crates = depset([crate for crate in crate_list if crate not in direct_crates])
 
     return DepInfo(
-        direct_crates = direct_crates,
+        direct_crates = depset(direct_crates),
         indirect_crates = indirect_crates,
         transitive_crates = transitive_crates,
         transitive_dylibs = transitive_dylibs,

rust/repositories.bzl

@@ -1,5 +1,5 @@
 load(":known_shas.bzl", "FILE_KEY_TO_SHA")
-load(":platform/triple_mappings.bzl", "system_to_binary_ext", "system_to_dylib_ext", "system_to_staticlib_ext", "triple_to_constraint_set", "triple_to_system")
+load("//rust/platform:triple_mappings.bzl", "system_to_binary_ext", "system_to_dylib_ext", "system_to_staticlib_ext", "triple_to_constraint_set", "triple_to_system")
 
 DEFAULT_TOOLCHAIN_NAME_PREFIX = "toolchain_for"