It's not possible to build linux 32 bit on 64 bit host machine with gn

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/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/toolchain.gni")
@@ skipping 476 matching lines @@
 # without using everything that "compiler" brings in.  Options that
 # tweak code generation for a particular CPU do not belong here!
 # See "compiler_codegen", below.
 config("compiler_cpu_abi") {
   cflags = []
   ldflags = []
 
   if (is_posix && !(is_mac || is_ios)) {
     # CPU architecture. We may or may not be doing a cross compile now, so for
     # simplicity we always explicitly set the architecture.
-    if (current_cpu == "x64") {
+    if (target_cpu == "x64") {

[Dirk Pranke, 2016/06/23 16:22:43]

I think these changes are wrong and the existing code is correct; these changes
will (should?) break binaries built with the host toolchain.

       cflags += [
         "-m64",
         "-march=x86-64",
       ]
       ldflags += [ "-m64" ]
-    } else if (current_cpu == "x86") {
+    } else if (target_cpu == "x86") {
       cflags += [ "-m32" ]
       ldflags += [ "-m32" ]
       if (!is_nacl) {
         cflags += [
           "-msse2",
           "-mfpmath=sse",
           "-mmmx",
         ]
       }
-    } else if (current_cpu == "arm") {
+    } else if (target_cpu == "arm") {
       if (is_clang && !is_android && !is_nacl) {
         cflags += [ "--target=arm-linux-gnueabihf" ]
         ldflags += [ "--target=arm-linux-gnueabihf" ]
       }
       if (!is_nacl) {
         cflags += [
           "-march=$arm_arch",
           "-mfloat-abi=$arm_float_abi",
         ]
         if (arm_use_thumb) {
           cflags += [ "-mthumb" ]
           if (is_android && !is_clang) {
             # Clang doesn't support this option.
             cflags += [ "-mthumb-interwork" ]
           }
         }
       }
       if (arm_tune != "") {
         cflags += [ "-mtune=$arm_tune" ]
       }
-    } else if (current_cpu == "arm64") {
+    } else if (target_cpu == "arm64") {
       if (is_clang && !is_android && !is_nacl) {
         cflags += [ "--target=aarch64-linux-gnu" ]
         ldflags += [ "--target=aarch64-linux-gnu" ]
       }
-    } else if (current_cpu == "mipsel") {
+    } else if (target_cpu == "mipsel") {
       if (is_clang) {
         # Temporarily needed due to unsupported MIPS macro instructions
         # in inline asm code in third_party projects (libwebp and webrtc).
         # TODO(lmilko) Enable integrated-as.
         cflags += [ "-fno-integrated-as" ]
       }
       if (mips_arch_variant == "r6") {
         if (is_clang) {
           cflags += [
             "--target=mipsel-linux-gnu",
@@ skipping 63 matching lines @@
         }
       }
 
       if (mips_dsp_rev == 1) {
         cflags += [ "-mdsp" ]
       } else if (mips_dsp_rev == 2) {
         cflags += [ "-mdspr2" ]
       }
 
       cflags += [ "-m${mips_float_abi}-float" ]
-    } else if (current_cpu == "mips64el") {
+    } else if (target_cpu == "mips64el") {
       if (mips_arch_variant == "r6") {
         if (is_clang) {
           if (is_android) {
             cflags += [
               "--target=mips64el-linux-android",
               "-march=mips64el",
               "-mcpu=mips64r6",
             ]
             ldflags += [ "--target=mips64el-linux-android" ]
           }
         } else {
           cflags += [
             "-mips64r6",
             "-Wa,-mips64r6",
           ]
           ldflags += [ "-mips64r6" ]
         }
       } else if (mips_arch_variant == "r2") {
         cflags += [
           "-mips64r2",
           "-Wa,-mips64r2",
         ]
         ldflags += [ "-mips64r2" ]
       }
-    } else if (current_cpu == "pnacl" && is_nacl_nonsfi) {
+    } else if (target_cpu == "pnacl" && is_nacl_nonsfi) {
       if (target_cpu == "x86" || target_cpu == "x64") {
         cflags += [
           "-arch",
           "x86-32-nonsfi",
           "--pnacl-bias=x86-32-nonsfi",
           "--target=i686-unknown-nacl",
         ]
         ldflags += [
           "-arch",
           "x86-32-nonsfi",
@@ skipping 879 matching lines @@
 
 if (is_ios || is_mac) {
   # On Mac and iOS, this enables support for ARC (automatic ref-counting).
   # See http://clang.llvm.org/docs/AutomaticReferenceCounting.html.
   config("enable_arc") {
     common_flags = [ "-fobjc-arc" ]
     cflags_objc = common_flags
     cflags_objcc = common_flags
   }
 }