Fix ARMv6 Linux cross-build

tools/gn.py

 #!/usr/bin/env python
 # Copyright 2016 The Dart project 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 argparse
 import multiprocessing
 import os
 import shutil
 import subprocess
@@ skipping 50 matching lines @@
 
 
 def GetOutDir(mode, arch, target_os):
   return utils.GetBuildRoot(HOST_OS, mode, arch, target_os)
 
 
 def ToCommandLine(gn_args):
   def merge(key, value):
     if type(value) is bool:
       return '%s=%s' % (key, 'true' if value else 'false')
+    elif type(value) is int:
+      return '%s=%d' % (key, value)
     return '%s="%s"' % (key, value)
   return [merge(x, y) for x, y in gn_args.iteritems()]
 
 
 def HostCpuForArch(arch):
   if arch in ['ia32', 'arm', 'armv6', 'armv5te', 'mips',
               'simarm', 'simarmv6', 'simarmv5te', 'simmips', 'simdbc',
               'armsimdbc']:
     return 'x86'
   if arch in ['x64', 'arm64', 'simarm64', 'simdbc64', 'armsimdbc64']:
@@ skipping 86 matching lines @@
     gn_args['dart_use_fallback_root_certificates'] = True
 
   gn_args['dart_zlib_path'] = "//runtime/bin/zlib"
 
   # Use tcmalloc only when targeting Linux and when not using ASAN.
   gn_args['dart_use_tcmalloc'] = ((gn_args['target_os'] == 'linux')
                                   and not UseSanitizer(args))
 
   if gn_args['target_os'] == 'linux':
     if gn_args['target_cpu'] == 'arm':
-      # Force -mfloat-abi=hard and -mfpu=neon for arm on Linux as we're
-      # specifying a gnueabihf compiler in //build/toolchain/linux BUILD.gn.
-      gn_args['arm_arch'] = 'armv7'
-      gn_args['arm_float_abi'] = 'hard'
+      # Default to -mfloat-abi=hard and -mfpu=neon for arm on Linux as we're
+      # specifying a gnueabihf compiler in //build/toolchain/linux/BUILD.gn.
+      floatabi = 'hard' if args.arm_float_abi == '' else args.arm_float_abi
+      gn_args['arm_version'] = 7
+      gn_args['arm_float_abi'] = floatabi
       gn_args['arm_use_neon'] = True
     elif gn_args['target_cpu'] == 'armv6':
-      raise Exception("GN support for armv6 unimplemented")
+      floatabi = 'softfp' if args.arm_float_abi == '' else args.arm_float_abi
+      gn_args['target_cpu'] = 'arm'
+      gn_args['arm_version'] = 6
+      gn_args['arm_float_abi'] = floatabi
     elif gn_args['target_cpu'] == 'armv5te':
       raise Exception("GN support for armv5te unimplemented")
 
   gn_args['is_debug'] = mode == 'debug'
   gn_args['is_release'] = mode == 'release'
   gn_args['is_product'] = mode == 'product'
   gn_args['dart_debug'] = mode == 'debug'
 
   # This setting is only meaningful for Flutter. Standalone builds of the VM
   # should leave this set to 'develop', which causes the build to defer to
@@ skipping 122 matching lines @@
       help='Build variants (comma-separated).',
       metavar='[all,debug,release,product]',
       default='debug')
   common_group.add_argument('--os',
       type=str,
       help='Target OSs (comma-separated).',
       metavar='[all,host,android]',
       default='host')
   common_group.add_argument("-v", "--verbose",
       help='Verbose output.',
-      default=False, action="store_true")
+      default=False,
+      action="store_true")
 
+  other_group.add_argument('--arm-float-abi',
+      type=str,
+      help='The ARM float ABI (soft, softfp, hard)',
+      metavar='[soft,softfp,hard]',
+      default='')
   other_group.add_argument('--asan',
       help='Build with ASAN',
       default=UseASAN(),
       action='store_true')
   other_group.add_argument('--no-asan',
       help='Disable ASAN',
       dest='asan',
       action='store_false')
   other_group.add_argument('--clang',
       help='Use Clang',
@@ skipping 115 matching lines @@
       return 1
 
   endtime = time.time()
   if args.verbose:
     print ("GN Time: %.3f seconds" % (endtime - starttime))
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv))