GN: Change the default meaning of dart_target_arch from current_cpu to target_cpu.

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 65 matching lines @@
 
 def HostCpuForArch(arch):
   if arch in ['ia32', 'arm', 'armv6', 'armv5te',
               'simarm', 'simarmv6', 'simarmv5te', 'simdbc',
               'armsimdbc']:
     return 'x86'
   if arch in ['x64', 'arm64', 'simarm64', 'simdbc64', 'armsimdbc64']:
     return 'x64'
 
 
+# The C compiler's target.
 def TargetCpuForArch(arch, target_os):
   if arch in ['ia32', 'simarm', 'simarmv6', 'simarmv5te']:
     return 'x86'
-  if arch in ['simarm64']:
+  if arch in ['x64', 'simarm64']:
     return 'x64'
   if arch == 'simdbc':
     return 'arm' if target_os == 'android' else 'x86'
   if arch == 'simdbc64':
     return 'arm64' if target_os == 'android' else 'x64'
   if arch == 'armsimdbc':
     return 'arm'
   if arch == 'armsimdbc64':
     return 'arm64'
   return arch
 
 
+# The Dart compiler's target.
+def DartTargetCpuForArch(arch):
+  if arch in ['ia32']:
+    return 'ia32'
+  if arch in ['x64']:
+    return 'x64'
+  if arch in ['arm', 'simarm']:
+    return 'arm'
+  if arch in ['armv6', 'simarmv6']:
+    return 'armv6'
+  if arch in ['armv5te', 'simarmv5te']:
+    return 'armv5te'
+  if arch in ['arm64', 'simarm64']:
+    return 'arm64'
+  if arch in ['simdbc', 'simdbc64', 'armsimdbc', 'armsimdbc64']:
+    return 'dbc'
+  return arch
+
+
 def HostOsForGn(host_os):
   if host_os.startswith('macos'):
     return 'mac'
   if host_os.startswith('win'):
     return 'win'
   return host_os
 
 
 # Where string_map is formatted as X1=Y1,X2=Y2 etc.
 # If key is X1, returns Y1.
@@ skipping 23 matching lines @@
 
 def ToGnArgs(args, mode, arch, target_os):
   gn_args = {}
 
   host_os = HostOsForGn(HOST_OS)
   if target_os == 'host':
     gn_args['target_os'] = host_os
   else:
     gn_args['target_os'] = target_os
 
-  gn_args['dart_target_arch'] = arch
+  gn_args['host_cpu'] = HostCpuForArch(arch)
   gn_args['target_cpu'] = TargetCpuForArch(arch, target_os)
-  gn_args['host_cpu'] = HostCpuForArch(arch)
+  gn_args['dart_target_arch'] = DartTargetCpuForArch(arch)
   crossbuild = gn_args['target_cpu'] != gn_args['host_cpu']
 
   if arch != HostCpuForArch(arch):
     # Training an app-jit snapshot under a simulator is slow. Use script
     # snapshots instead.
     gn_args['dart_snapshot_kind'] = 'script'
   else:
     gn_args['dart_snapshot_kind'] = 'app-jit'
 
   # We only want the fallback root certs in the standalone VM on
@@ skipping 307 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))