Revert "Don't require a RISC-V libc and crt when configuring (#132)" (#140)

This reverts commit a02257a861a4d13f31868a27c197cfc5576101e1.

Don't require a RISC-V libc and crt when configuring (#132)

Fix stubs-lp64.h/stubs-lp64d.h/stubs-ilp32.h/stubs-ilp32d.h not found

For now, we always compile files with -mabi option by using
soft-fp ABI. But there are some files use the header which in
toolchain, like unistd.h, stdint.h and so on. Finally, these
header files include other header files which existing depend
on ABI such as stubs-lp64.h or stubs-lp64d.h. So it causes the
header file not found when using the double-float toolchain with
soft-float ABI.

Fix up by compiling files with -march and -mabi options only if
there is specifying the --with-arch option at configure time.

If use the --with-arch option at configure time, that means your
toolchain has multi-lib support, so always building riscv-pk
by soft-float ABI is fine. Otherwise, we don't compile files with
specifying march and mabi options explicitly

Properly license all nontrivial files

Replace the --enable-32bit option by --with-arch

Get rid of the --enable-32bit option and switch to use --with-arch,
which is more standard because it matches the GCC build.

If --with-arch is not specified, it defaults to whatever the
compiler's default is.

The --with-abi is not necessary for this project.
Unconditionally compile it with a no-float ABI.

Fix line endings in the logo

Allow users to pick a logo

Don't block for acks on console writes

Support 32bit build (#27)

* Support configuration for a 32-bit build.

* Regenerate configure.

Refactor pk, bbl, machine into separate libraries

Yuck.

Don't automatically run autoconf

Run it yourself if you modify configure.ac, and commit the configure script.

Change the behavior of the DESTDIR make variable

DESTDIR is a common make idiom. As per the GNU coding standards

https://www.gnu.org/prep/standards/html_node/DESTDIR.html

"DESTDIR is a variable prepended to each installed target file, like
this:

$(INSTALL_PROGRAM) foo $(DESTDIR)$(bindir)/foo
$(INSTALL_DATA) libfoo.a $(DESTDIR)$(libdir)/libfoo.a

The DESTDIR variable is specified by the user on the make command
line as an absolute file name. For example:

make DESTDIR=/tmp/stage install

DESTDIR should be supported only in the install* and uninstall*
targets, as those are the only targets where it is useful.

If your installation step would normally install /usr/local/bin/foo
and /usr/local/lib/libfoo.a, then an installation invoked as in the
example above would install /tmp/stage/usr/local/bin/foo and
/tmp/stage/usr/local/lib/libfoo.a instead."

The current Makefile.in uses DESTDIR, but has a slightly non-standard
behavior: the target install location doesn't include "$prefix". This
breaks package managers, because stuff ends up getting installed to
the wrong location.

Unfortunately the only way I can think of to fix this involves
silently changing the behavior of DESTDIR. Hopefully nobody is using
it...?

[port of 8a2088b59162fe16c16d26ddc1cfcaaaa8c4156f in riscv-fesvr]

Split pk functionality into pk and bbl

pk is now an AEE only (i.e. it can only execute user programs).
bbl is now an SEE only (i.e. it can only host kernels).

Don't rely on the C library

respect CFLAGS and LDFLAGS env vars

temporary undoing of renaming

Renamed packages

[pk] load pk at addr 0; user stack top = MEMSIZE

[opcodes, pk, sim, xcc] made jumps shorter and PC-relative

[pk, sim] added FPU emulation support to proxy kernel

[pk,fesvr] improved proxykernel build system

Now uses a modified MCPPBS. Add --host=riscv to configure path.

Front-end server now just searches PATH for riscv-pk, so just install the pk
to somewhere in your path.