Rather than stuffing the command line with a bunch of -D flags, start
moving things to config.h which is managed by autoheader. This makes
the makefile a bit simpler and the build output tighter, and it makes
the migration to automake easier as there are fewer vars to juggle.
We'll want to move the other options out too, but it'll take more work.
The common subdir sets up a cconfig.h file to hold checks for the common
code. In practice, most files still end up using config.h instead which
just leads to confusion.
Merge all the configure checks that went into cconfig.h into SIM_AC_COMMON
so we can drop the cconfig.h file altogether. Now there is only a single
config.h file like normal.
The --enable-sim-hostendian flag was purely so people had an escape route
for when cross-compiling. This is because historically, AC_C_BIGENDIAN
did not work in those cases. That was fixed a while ago though, so we can
require that macro everywhere now and simplify a good bit of code.
No arch is using this anymore, and we want all new ports using the
hardware framework instead. Punt WITH_DEVICES and the two callbacks
device_io_{read,write}_buffer.
We can also punt the tconfig.h file as no port is using it anymore.
This fixes in-tree builds that get confused by picking up the wrong
one (common/ vs <port>/) caused by commit ae7d0cac8c.
Any port that needs to set up a global define can use their own
sim-main.h file that they must provide regardless.
Rather than manually include tconfig.h when we think we'll need it (which
is error prone as it can define symbols we expect from config.h), have it
be included directly by config.h. Since we know we have to include that
header everywhere already, this will make sure tconfig.h isn't missed.
It should also be fine as tconfig.h is supposed to be simple and only set
up a few core defines for the target.
This allows us to stop symlinking it in place all the time and just use
it straight out of the respective source directory.
