[SeaBIOS] [PATCH] Makefile: Allow to override CPP variable

[Kevin O'Connor]

On Sat, May 23, 2015 at 04:15:47PM +0200, Paul Menzel wrote:
> Date: Sat, 23 May 2015 16:02:08 +0200
> 
> Using the conditional assignment operator `?=` [1] instead of `=` makes
> it possible to override the variable `CPP` by using an environment
> variable
> 
> 	$ CPP=cpp-5 make
> 
> or directly setting it.
> 
> 	$ make CPP=cpp-5

I think picking up build definitions from the environment is
confusing.  The second form you show above should work today, and I
think it is sufficient for those needing to override build
definitions.

-Kevin