Allow targets to override the output directory.

build/toolchain/gcc_toolchain.gni

 # 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.
 
 import("//build/config/nacl/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ skipping 216 matching lines @@
 
       # This needs a Python script to avoid using simple sh features in this
       # command, in case the host does not use a POSIX shell (e.g. compiling
       # POSIX-like toolchains such as NaCl on Windows).
       ar_wrapper =
           rebase_path("//build/toolchain/gcc_ar_wrapper.py", root_build_dir)
       command = "$python_path \"$ar_wrapper\" --output={{output}} --ar=\"$ar\" $arflags rcsD @\"$rspfile\""
       description = "AR {{output}}"
       rspfile_content = "{{inputs}}"
       outputs = [
-        "{{target_out_dir}}/{{target_output_name}}{{output_extension}}",
+        "{{output_dir}}/{{target_output_name}}{{output_extension}}",
       ]
+
+      # Shared libraries go in the target out directory by default so we can
+      # generate different targets with the same name and not have them collide.
+      default_output_dir = "{{target_out_dir}}"
       default_output_extension = ".a"
       output_prefix = "lib"
     }
 
     tool("solink") {
       soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
-      sofile = "{{root_out_dir}}/$soname"  # Possibly including toolchain dir.
-      if (shlib_subdir != ".") {
-        sofile = "{{root_out_dir}}/$shlib_subdir/$soname"
-      }
+      sofile = "{{output_dir}}/$soname"  # Possibly including toolchain dir.
       rspfile = sofile + ".rsp"
 
-      unstripped_sofile = sofile
       if (defined(invoker.strip)) {
         unstripped_sofile = "{{root_out_dir}}/lib.unstripped/$soname"
+      } else {
+        unstripped_sofile = sofile
       }
 
       # These variables are not built into GN but are helpers that
       # implement (1) linking to produce a .so, (2) extracting the symbols
       # from that file (3) if the extracted list differs from the existing
       # .TOC file, overwrite it, otherwise, don't change it.
       tocfile = sofile + ".TOC"
 
       link_command = "$ld -shared {{ldflags}} -o \"$unstripped_sofile\" -Wl,-soname=\"$soname\" @\"$rspfile\""
 
@@ skipping 12 matching lines @@
 
       rspfile_content = "-Wl,--whole-archive {{inputs}} {{solibs}} -Wl,--no-whole-archive $solink_libs_section_prefix {{libs}} $solink_libs_section_postfix"
 
       description = "SOLINK $sofile"
 
       # 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 = default_shlib_extension
 
+      default_output_dir = "{{root_out_dir}}"
+      if (shlib_subdir != ".") {
+        default_output_dir += "/$shlib_subdir"
+      }
+
       output_prefix = "lib"
 
       # Since the above commands only updates the .TOC file when it changes, ask
       # Ninja to check if the timestamp actually changed to know if downstream
       # dependencies should be recompiled.
       restat = true
 
       # Tell GN about the output files. It will link to the sofile but use the
       # tocfile for dependency management.
       outputs = [
         sofile,
         tocfile,
       ]
       if (sofile != unstripped_sofile) {
         outputs += [ unstripped_sofile ]
       }
       link_output = sofile
       depend_output = tocfile
     }
 
     tool("solink_module") {
       soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
-      sofile = "{{root_out_dir}}/$soname"  # Possibly including toolchain dir.
-      if (shlib_subdir != ".") {
-        sofile = "{{root_out_dir}}/$shlib_subdir/$soname"
-      }
+      sofile = "{{output_dir}}/$soname"
       rspfile = sofile + ".rsp"
 
-      unstripped_sofile = sofile
       if (defined(invoker.strip)) {
         unstripped_sofile = "{{root_out_dir}}/lib.unstripped/$soname"
+      } else {
+        unstripped_sofile = sofile
       }
 
       command = "$ld -shared {{ldflags}} -o \"$unstripped_sofile\" -Wl,-soname=\"$soname\" @\"$rspfile\""
 
       if (defined(invoker.strip)) {
         strip_command = "${invoker.strip} --strip-unneeded -o \"$sofile\" \"$unstripped_sofile\""
         command += " && " + strip_command
       }
       rspfile_content = "-Wl,--whole-archive {{inputs}} {{solibs}} -Wl,--no-whole-archive $solink_libs_section_prefix {{libs}} $solink_libs_section_postfix"
 
       description = "SOLINK_MODULE $sofile"
 
       # Use this for {{output_extension}} expansions unless a target manually
       # overrides it (in which case {{output_extension}} will be what the target
       # specifies).
       if (defined(invoker.loadable_module_extension)) {
         default_output_extension = invoker.loadable_module_extension
       } else {
         default_output_extension = default_shlib_extension
       }
 
+      default_output_dir = "{{root_out_dir}}"
+      if (shlib_subdir != ".") {
+        default_output_dir += "/$shlib_subdir"
+      }
+
       output_prefix = "lib"
 
       outputs = [
         sofile,
       ]
       if (sofile != unstripped_sofile) {
         outputs += [ unstripped_sofile ]
       }
     }
 
     tool("link") {
       exename = "{{target_output_name}}{{output_extension}}"
-      outfile = "{{root_out_dir}}/$exename"
+      outfile = "{{output_dir}}/$exename"
       rspfile = "$outfile.rsp"
       unstripped_outfile = outfile
 
       # 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 = default_executable_extension
 
+      default_output_dir = "{{root_out_dir}}"
+
       if (defined(invoker.strip)) {
         unstripped_outfile = "{{root_out_dir}}/exe.unstripped/$exename"
       }
 
       command = "$ld {{ldflags}} -o \"$unstripped_outfile\" -Wl,--start-group @\"$rspfile\" {{solibs}} -Wl,--end-group $libs_section_prefix {{libs}} $libs_section_postfix"
       if (defined(invoker.strip)) {
         link_wrapper =
             rebase_path("//build/toolchain/gcc_link_wrapper.py", root_build_dir)
         command = "$python_path \"$link_wrapper\" --strip=\"${invoker.strip}\" --unstripped-file=\"$unstripped_outfile\" --output=\"$outfile\" -- $command"
       }
@@ skipping 90 matching lines @@
     nm = "${toolprefix}nm"
 
     forward_variables_from(invoker,
                            [
                              "toolchain_cpu",
                              "toolchain_os",
                              "use_gold",
                            ])
   }
 }