Add support for sysroots to GN's pkg-config.

build/config/compiler/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.
 
 import("//build/config/linux/sysroot.gni")
 
 # Base compiler configuration.
 config("compiler") {
   include_dirs = [ "//", root_gen_dir ]
   if (is_win) {
@@ skipping 65 matching lines @@
       ]
     } else {
       # Non-Mac Posix compiler flags setup.
       # -----------------------------------
 
       # CPU architecture. We may or may not be doing a cross compile now, so for
       # simplicity we always explicitly set the architecture.
       if (cpu_arch == "x64") {
         cflags += "-m64"
         ldflags += "-m64"
-      } else if (cpu_arch == "x32") {
+      } else if (cpu_arch == "x86") {
         cflags += "-m32"
         ldflags += "-m32"
       }
     }
 
     # Linux-specific compiler flags setup.
     # ------------------------------------
     if (is_linux) {
       cflags += [
         "-fPIC",
@@ skipping 21 matching lines @@
           # Only apply this to the target linker, since the host
           # linker might not be gold, but isn't used much anyway.
           "-Wl,--threads",
           "-Wl,--thread-count=4",
         ]
       }
 
       if (sysroot != "") {
         cflags += "--sysroot=" + sysroot
         ldflags += "--sysroot=" + sysroot
+
+        # Need to get some linker flags out of the sysroot.
+        ldflags += exec_script("../linux/sysroot_ld_path.py",
+            [rebase_path("../../linux/sysroot_ld_path.sh", ".", root_build_dir),
+             sysroot],
+            "value")
       }
 
       ldflags += [
         "-fPIC",
         "-pthread",
         "-Wl,-z,noexecstack",
         "-Wl,-z,now",
         "-Wl,-z,relro",
       ]
     }
@@ skipping 271 matching lines @@
   } else {
     cflags = [ "-g1" ]
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }