Update ARMGCC to support cross/native compilation.

The ARMGCC target currently has hard-wired toolchain
binary names (arm-none-eabi-*). This is quite unflexible,
does not match all existing compatible cross-toolchains and does not
permit cross-compiling at all.

This patch makes the ARMGCC target use the CROSS_COMPILE
environment variable, just like the Linux kernel, as a full prefix to the
actual toolchain binaries. Omitting or unsetting CROSS_COMPILE will make
both targets equivalent to ELFGCC, enabling native builds on ARM platforms..

It will break existing build scripts, but the fix would be a one-line
change of an environment variable.

Signed-off-by: leif.lindholm@linaro.org
Reviewed-by: Olivier Martin <olivier.martin@arm.com>



git-svn-id: https://edk2-buildtools.svn.sourceforge.net/svnroot/edk2-buildtools/trunk/BaseTools@2580 c2973edb-eda0-4c78-bc6a-9341b269661f
Enable native ARM builds of BaseTools

This patch, incoorporating some earlier work by John.Rigby@linaro.org,
enables full support for the BaseTools on ARM platforms - for building
edk2 natively under ARM Linux.

Signed-off-by: leif.lindholm@linaro.org
Reviewed-by: Olivier Martin <olivier.martin@arm.com>



git-svn-id: https://edk2-buildtools.svn.sourceforge.net/svnroot/edk2-buildtools/trunk/BaseTools@2581 c2973edb-eda0-4c78-bc6a-9341b269661f