Bump Bazel to 1.0.0.

Had to add `ar_files` and `as_files` to the toolchain rule. See:
bazelbuild/bazel#8531

Tried breaking up the filegroups, but the toolchain is too convoluted to be
worth it. Found out along the way, though, that the "cpp" `tool_path` pointed
to the wrong binary name, so fixed that.

.bazeliskrc

@@ -1 +1 @@
-USE_BAZEL_VERSION=0.27.0
+USE_BAZEL_VERSION=1.0.0

toolchain/BUILD

@@ -9,28 +9,34 @@ cc_toolchain_suite(
 )
 
 filegroup(
-    name = "all",
+    name = "toolchain_files",
     srcs = [
+        "@nacl_sdk//:pnacl_includes",
+        "@nacl_sdk//:pnacl_toolchain",
+        "pnacl_ar.sh",
+        "pnacl_clang++.sh",
         "pnacl_clang.sh",
         "pnacl_ld.sh",
-        "pnacl_ar.sh",
-        "pnacl_cpp.sh",
-        "pnacl_nm.sh",
         "pnacl_strip.sh",
-        "@nacl_sdk//:pnacl_all_files",
     ],
 )
 
+filegroup(name = "empty")
+
 cc_toolchain(
     name = "pnacl_toolchain",
     toolchain_identifier = "pnacl-toolchain",
     toolchain_config = ":pnacl_toolchain_config",
-    all_files = ":all",
-    compiler_files = ":all",
-    dwp_files = ":all",
-    linker_files = ":all",
-    objcopy_files = ":all",
-    strip_files = ":all",
+    ar_files = ":toolchain_files",
+    compiler_files = ":toolchain_files",
+    linker_files = ":toolchain_files",
+    strip_files = ":toolchain_files",
+
+    # The following are no longer used, but still must exist.
+    all_files = ":empty",
+    dwp_files = ":empty",
+    objcopy_files = ":empty",
+
     supports_param_files = 0,
 )
 

toolchain/pnacl_clang++.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+set -euo pipefail
+external/nacl_sdk/toolchain/linux_pnacl/bin/pnacl-clang++ "$@"

toolchain/pnacl_toolchain_config.bzl

@@ -22,7 +22,7 @@ def _impl(ctx):
         ),
         tool_path(
             name = "cpp",
-            path = "pnacl_cpp.sh",
+            path = "pnacl_clang++.sh",
         ),
         tool_path(
             name = "gcov",