Move to Bazel 0.23.0.

This is the last version of Bazel to support the use of the CROSSTOOL file. The
next upgrade migth be a doozy.

It was necessary to bump the version of protobuf in order to get past some
deprecated usage:
bazelbuild/bazel#5827

This further necessitated adding some transitive dependencies. (This is solved
more properly in a later version of protobuf, but moving that far came with a
number of other challenges.) This also required setting
`-Wno-inconsistent-missing-override`; I hope that warning can be restored in
the future.

.bazeliskrc

@@ -1 +1 @@
-USE_BAZEL_VERSION=0.20.0
+USE_BAZEL_VERSION=0.23.0

CROSSTOOL

@@ -99,6 +99,8 @@ toolchain {
   compiler_flag: "-Wall"
   # All warnings are errors.
   compiler_flag: "-Werror"
+  # Protobufs won't build with this warning:
+  compiler_flag: "-Wno-inconsistent-missing-override"
   # Would be nice to enable this warning, but then protobufs won't build.
   #compiler_flag: "-Wunused-parameter"
   # But disable some that are problematic.

WORKSPACE

@@ -64,13 +64,19 @@ http_archive(
 )
 
 http_archive(
-    name = "zlib",
+    name = "pnacl_zlib",
     url = "https://gsdview.appspot.com/webports/builds/pepper_49/trunk-785-g807a23e/packages/zlib_1.2.8_pnacl.tar.bz2",
     sha256 = "99203f49edad39570a3362e72373ea1d63a97b9b1828b75e45d3e856d2832033",
     strip_prefix = "payload",
     build_file = "BUILD.zlib",
 )
 
+# Needed by `com_google_protobuf`.
+bind(
+    name = "zlib",
+    actual = "@pnacl_zlib//:zlib",
+)
+
 http_archive(
     name = "glibc_compat",
     url = "https://gsdview.appspot.com/webports/builds/pepper_49/trunk-785-g807a23e/packages/glibc-compat_0.1_pnacl.tar.bz2",
@@ -105,7 +111,15 @@ new_git_repository(
 git_repository(
     name = "com_google_protobuf",
     remote = "https://github.com/google/protobuf.git",
-    commit = "ce044817c7ba0aea27c3fd8e496635d94d20a755", # tag = "v3.6.0.1"
+    commit = "582743bf40c5d3639a70f98f183914a2c0cd0680", # tag = "v3.7.0"
+)
+
+# Needed by `com_google_protobuf`.
+http_archive(
+    name = "bazel_skylib",
+    sha256 = "bbccf674aa441c266df9894182d80de104cabd19be98be002f6d478aaa31574d",
+    strip_prefix = "bazel-skylib-2169ae1c374aab4a09aa90e65efe1a3aad4e279b",
+    urls = ["https://github.com/bazelbuild/bazel-skylib/archive/2169ae1c374aab4a09aa90e65efe1a3aad4e279b.tar.gz"],
 )
 
 git_repository(

external/BUILD.libssh

@@ -22,7 +22,7 @@ cc_library(
         ":pnacl_mode": [
             "@glibc_compat//:glibc_compat",
             "@openssl//:openssl",
-            "@zlib//:zlib",
+            "@pnacl_zlib//:zlib",
         ],
         "//conditions:default": [
             ":local_openssl",

external/BUILD.mosh

@@ -110,7 +110,7 @@ cc_library(
     deps = [
         ":crypto_lib",
         ":protos_lib",
-        "@zlib//:zlib",
+        "@pnacl_zlib//:zlib",
     ],
     includes = ["src/network"],
 )