Missing features.h in chromium

[bob prohaska]

Just for fun I've tried compiling www/chromium on an RPI2 by simply adding armv6 
to the list of achitechtures. This is on -head from last night.

It got far enough to report:

In file included from ../../v8/src/base/accounting-allocator.cc:5:
In file included from ../../v8/src/base/accounting-allocator.h:8:
In file included from ../../v8/src/base/atomicops.h:29:
In file included from ../../v8/src/base/build_config.h:8:
../../v8/include/v8config.h:16:11: fatal error: 'features.h' file not found
# include <features.h>
          ^
1 error generated.
ninja: build stopped: subcommand failed.

It isn't obvious to me that this is an architecture-related error, might
there be a fix or workaround? 

Thanks for reading,

bob prohaska