Failure building HEAD in libraries/base/Data/ByteString.hs

[Simon Marlow]

Donald Bruce Stewart wrote:
> Simon, how do you want to proceed with this? Just add
> -fno-builtin-strlen to the .hc bootstrappping CC flags?

Added -fno-builtin to PLATFORM_HC_BOOT_CC_OPTS in mk/bootstrap.mk.

Cheers,
	Simon