Add go_bootstrap toolchain target

Summary:
Got an error when testing build of facebookincubator/phabtest_rust. Adding this
target to the shims seems to fix it.

Reviewed By: bigfootjon

Differential Revision: D64618954

fbshipit-source-id: 4ea6b868647ea450a330b82b51eb94707ffa40cb

shim/BUCK

@@ -7,7 +7,7 @@
 
 load("@prelude//toolchains:cxx.bzl", "system_cxx_toolchain")
 load("@prelude//toolchains:genrule.bzl", "system_genrule_toolchain")
-load("@prelude//toolchains:go.bzl", "system_go_toolchain")
+load("@prelude//toolchains:go.bzl", "system_go_bootstrap_toolchain", "system_go_toolchain")
 load("@prelude//toolchains:haskell.bzl", "system_haskell_toolchain")
 load("@prelude//toolchains:ocaml.bzl", "system_ocaml_toolchain")
 load("@prelude//toolchains:python.bzl", "system_python_bootstrap_toolchain", "system_python_toolchain")
@@ -38,6 +38,11 @@ system_go_toolchain(
     visibility = ["PUBLIC"],
 )
 
+system_go_bootstrap_toolchain(
+    name = "go_bootstrap",
+    visibility = ["PUBLIC"],
+)
+
 system_haskell_toolchain(
     name = "haskell",
     visibility = ["PUBLIC"],