FreeCalypso loadtools have been designed from the beginning to work through
the Calypso chip's own boot ROM.  This approach works great for Openmoko and
Pirelli targets, but Compal phones unfortunately have this Calypso boot ROM
disabled at the board level.  To run our own code in these phones instead of
booting the regular firmware, we need to go through Compal's own boot code.
The latter allows loading code into IRAM and jumping to it, but not in the
same way as how we do it through the Calypso boot ROM.

One could argue that the "proper" way to support these Compal phones would be
to build a different version of our loadagent that is designed to be loaded
through Compal's boot code instead of the Calypso boot ROM, and then redesign
our fc-loadtool and fc-xram utilities to work with different loadagents loaded
in different ways on different target devices.  But I don't feel like doing
that - too invasive to the once-clean design of loadtools.

Hence I am adopting a different solution that works in the same way as
OsmocomBB's "chain loading": the IRAM image that is fed to Compal's boot code
is not our real loadagent, but a tiny piece of code that enables the Calypso
boot ROM and jumps to it.  All loadtools host programs will include this
optional "Compal stage" at the beginning, enabled for targets that need it,
but will then always fall into the Calypso boot ROM IRAM download path.

The approach I'm adopting is doubly inefficient for Mot C139/140 phones whose
bootloader effectively requires that the downloaded image be ~15 KiB long
even when we only need to download 32 bytes.  But hey, our ultimate goal is to
produce our own Calypso phones, rather than hack those made by diabolical
manufacturers who do not Respect Your Freedom; running our own gsm-fw on the
Mot C139 is only a transitional step, so making fc-loadtool/fc-xram entry
slower by a second or two is probably an acceptable price for keeping the
code clean for the boot-ROM-enabled free world.

In this directory we build the several different versions of compalstage
needed for different C1xx models.