README: improve description of compiler requirements

People run into "building bootblock without the required toolchain" too often.
Update documentation so they don't try to use random compilers to build
coreboot.

Change-Id: I9715b52a4bac9b886cc5627add074c04e06a0828
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/11047
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

0 files changed, 0 insertions, 0 deletions