Use destdir/rumprun-$MACHINE_GNU_ARCH$ as a GNU-like prefix.

Use MACHINE_GNU_ARCH, not MACHINE_ARCH

That matches the terms (and make variables!) with the NetBSD
Makefiles and avoids mismatch lossage.

Make it rumprun[-MACHINE_ARCH[-PLATFORM]]

That way MACHINE_ARCH (if it exists in the particular name),
is always in the same spot, and the same holds for PLATFORM.

create the bmk.ldscript link into objdir

call it rumprun.o, install into rumprun-platform-arch

Update header location to re-fix kernonly test

kernonly test: change -L to match new reality.

Build libs into objdir.

Well, the ones built by platform/Makefile.inc, at any rate.

Fix pasto in previous to fix kernonly build.

create main object and pseudostubs into objdir

Consolidate the RUMPRUN_MKCONF include dance into global.mk

Convert all safe-looking locations, i.e. NOT app-tools
or platform/xen/xen.

create config.mk into objdir

Simplify nolibc Makefile

No architecture specific ifdefs needed anymore, we can reuse
BUILDRUMP_TOOLFLAGS for i386.

Specify bake-time special ldflags in global.mk

Finally decouples Makefile.app-tools from platform/x/Makefile

make "make clean" work for non-hw without PLATFORM=foo

g/c libs which are now included in $rumprun.o

Put ldscript in common place

allow specifying platform as a make variable

default: hw

Fix test build for kernonly mode

Add tests and -k flag to buildtests.sh