Cross compile rules update

[Loïc Minier]

On Mon, Oct 11, 2010, Jan, Sebastien wrote:
> Either ways you expect to retrieve the cross-compiler name through the
> DEB_HOST_GNU_TYPE variable? In my case I always get
> DEB_HOST_GNU_TYPE=arm-linux-gnueabi (that's the output of
> dpkg-architecture). Is this expected?
> If yes, I don't understand how my cross-compiler (CS here) gets passed
> to make. Your two above proposals would override what I could write on
> the command line? (hence my 1st patch)

 So for Debian/Ubuntu-style cross-builds (dpkg-buildpackage -aarmel), we
 can assume that the cross-toolchain is using the $(DEB_HOST_GNU_TYPE)-
 prefix, so $(DEB_HOST_GNU_TYPE)-gcc, -ld etc. are available.

 It's however convenient for some specific packages, like the kernel or
 u-boot or x-loader, to be able to override the standard
 cross-compilation toolchain with a personal one.  In your case, the
 arm-none-linux-gnueabi- prefix or something like that.

 So the intent was to set CROSS_COMPILE to $(DEB_HOST_GNU_TYPE)- by
 default (standard Debian/Ubuntu cross builds) unless if CROSS_COMPILE
 is set (in which case, just use what's in CROSS_COMPILE instead).

 Note the ?= in my proposals which means that CROSS_COMPILE is only set
 if it wasn't set in the environment.

-- 
Loïc Minier