[build] Remove unused split_static_library.gni

The file was moved into the V8 repository:
https://crrev.com/c/1897826

Bug: v8:9911,857060
Change-Id: Ic7de59df826eef5b55778db335c21fa852d491c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1899456Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712983}

build/split_static_library.gni

-# Copyright 2016 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-import("//build/config/compiler/compiler.gni")
-
-template("split_static_library") {
-  assert(defined(invoker.split_count),
-         "Must define split_count for split_static_library")
-
-  # In many conditions the number of inputs will be 1 (because the
-  # count will be conditional on platform or configuration) and for
-  # some build configurations it's unnecessary to split libraries
-  # since the tooling will never create files of a problematic size.
-  if (invoker.split_count == 1 || use_lld) {
-    static_library(target_name) {
-      forward_variables_from(invoker, "*")
-    }
-  } else {
-    group_name = target_name
-
-    generated_static_libraries = []
-    current_library_index = 0
-    foreach(current_sources, split_list(invoker.sources, invoker.split_count)) {
-      current_name = "${target_name}_$current_library_index"
-      assert(
-          current_sources != [],
-          "Your values for splitting a static library generate one that has no sources.")
-      generated_static_libraries += [ ":$current_name" ]
-
-      static_library(current_name) {
-        # Generated static library shard gets everything but sources (which
-        # we're redefining) and visibility (which is set to be the group
-        # below).
-        forward_variables_from(invoker,
-                               "*",
-                               [
-                                 "check_includes",
-                                 "sources",
-                                 "visibility",
-                               ])
-        sources = current_sources
-        visibility = [ ":$group_name" ]
-
-        # When splitting a target's sources up into a series of static
-        # libraries, those targets will naturally include headers from each
-        # other arbitrarily. We could theoretically generate a web of
-        # dependencies and allow_circular_includes_from between all pairs of
-        # targets, but that's very cumbersome. Typical usage in Chrome is that
-        # only official Windows builds use split static libraries due to the
-        # Visual Studio size limits, and this means we'll still get header
-        # checking coverage for the other configurations.
-        check_includes = false
-
-        # Uniquify the output name if one is specified.
-        if (defined(invoker.output_name)) {
-          output_name = "${invoker.output_name}_$current_library_index"
-        }
-      }
-
-      current_library_index = current_library_index + 1
-    }
-
-    group(group_name) {
-      public_deps = generated_static_libraries
-      forward_variables_from(invoker,
-                             [
-                               "testonly",
-                               "visibility",
-                             ])
-    }
-  }
-}
-
-set_defaults("split_static_library") {
-  configs = default_compiler_configs
-}