[GN] Add solink_module tool on the Mac, Win, and GCC toolchains.

build/toolchain/mac/BUILD.gn

 # Copyright (c) 2013 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.
 
 # TODO(brettw) Use "gcc_toolchain.gni" like the Linux toolchains. This requires
 # some enhancements since the commands on Mac are slightly different than on
 # Linux.
 
 import("../goma.gni")
 import("//build/config/ios/ios_sdk.gni")
@@ skipping 149 matching lines @@
       # Tell GN about the output files. It will link to the dylib but use the
       # tocname for dependency management.
       outputs = [
         dylib,
         tocname,
       ]
       link_output = dylib
       depend_output = tocname
     }
 
+    tool("solink_module") {
+      sofile = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"  # eg "./libfoo.so"
+      rspfile = sofile + ".rsp"
+
+      link_command = "$ld -bundle {{ldflags}} -o $sofile -Wl,-filelist,$rspfile"
+      if (is_component_build) {
+        link_command += " -Wl,-install_name,@rpath/{{target_output_name}}{{output_extension}}"
+      }
+      link_command += " {{solibs}} {{libs}}"
+      command = link_command
+
+      rspfile_content = "{{inputs_newline}}"
+
+      description = "SOLINK_MODULE {{output}}"
+
+      # Use this for {{output_extension}} expansions unless a target manually
+      # overrides it (in which case {{output_extension}} will be what the target
+      # specifies).
+      default_output_extension = ".so"
+
+      output_prefix = "lib"
+
+      outputs = [
+        sofile,
+      ]
+    }
+
     tool("link") {
       outfile = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"
       rspfile = "$outfile.rsp"
       command = "$ld {{ldflags}} -o $outfile -Wl,-filelist,$rspfile {{solibs}} {{libs}}"
       description = "LINK $outfile"
       rspfile_content = "{{inputs_newline}}"
       outputs = [
         outfile,
       ]
     }
@@ skipping 70 matching lines @@
 }
 
 mac_toolchain("x64") {
   toolchain_cpu = "x64"
   toolchain_os = "mac"
   cc = "${goma_prefix}/gcc"
   cxx = "${goma_prefix}/g++"
   ld = cxx
   is_clang = false
 }