Fix host_arch detection for AIX and one new warning as error

build/detect_v8_host_arch.py

Index: build/detect_v8_host_arch.py
diff --git a/build/detect_v8_host_arch.py b/build/detect_v8_host_arch.py
index 3460a9a404f0ce459e6a3ac4f159cf6b06afb0d0..89e8286e1fdb459c7d475cfeef60efed684ef256 100644
--- a/build/detect_v8_host_arch.py
+++ b/build/detect_v8_host_arch.py
@@ -41,6 +41,7 @@ def DoMain(_):
   """Hook to be called from gyp without starting a separate python
   interpreter."""
   host_arch = platform.machine()
+  host_system = platform.system();
 
   # Convert machine type to format recognized by gyp.
   if re.match(r'i.86', host_arch) or host_arch == 'i86pc':
@@ -56,6 +57,13 @@ def DoMain(_):
   elif host_arch.startswith('mips'):
     host_arch = 'mipsel'
 
+  # Under AIX the value returned by platform.machine is not
+  # the best indicator of the host architecture
+  # AIX 6.1 which is the lowest level supported only provides
+  # a 64 bit kernel
+  if host_system == 'AIX':
+    host_arch = 'ppc64'
+
   # platform.machine is based on running kernel. It's possible to use 64-bit
   # kernel with 32-bit userland, e.g. to give linker slightly more memory.
   # Distinguish between different userland bitness by querying