In case of x86 arch, the target_arch variables passed through
GYP_DEFINES is also x86. But, this value is not recognized by gyp files,
so we need to pass ia32 instead. For x86 arch, we need to pass the value
of DEST_CPU, which is ia32.

Signed-off-by: Robert Chiras <robert.chiras@intel.com>

In execSync/execFileSync commands, we better verify the stderr buffer
from ret. In case of other exceptions thrown by spawnSync this buffer
might be null. If we don't check it and try to write it to process.stderr
we will end up throwing an irrelevant exception from Socket.write,
masking the initial exception which might show what is actually wrong
with spawnSync. Such an exception was hidden, when running this test on
Android. The exception was about '/bin/sh' not found, since in Android,
sh can be found in '/system/bin/sh'.

Signed-off-by: Robert Chiras <robert.chiras@intel.com>

`/bin/sh` does not exist on Android but `/system/bin/sh` does.

PR-URL: nodejs#6745
Refs: nodejs#6733
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>

`/bin/sh` does not exist on Android but `/system/bin/sh` does.

PR-URL: #6745
Refs: #6733
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>