Add further -no-pie checks to Rumprun build tools

This builds upon the previous commit to add -no-pie anywhere the
relocatable flag (-Wl,-r) is used to handle compilers that enable -pie
by default (Such as Debian Stretch).

cc: exit with success if nothing fails

cc: make output of -dump{machine,specs} match reality

app-tools cc: fail for -print-multiarch

Some packages (e.g. python) will do the wrong thing if the
compiler pretends to support multiarch.

with thanks to @rday

app-tools cc: use basename $0 for error, not whole $0

set --sysroot for compiler wrapper

Makes cc -print-sysroot work. That said, why do we still
need -isystem and -L in our specs? (yes, I tried without them,
lossage generated)

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.

Install specs to lib instead of share root.

specs are now split into arch and machine specs.

Install brprintmetainfo, it's used by cc

Fixes all kinds of problems in not detecting compile failures.

Problem reported by meena on irc.

Use more consistent !REPLACE! pattern names.

install toolchain to destdir

Make sure -lc++ comes before -lunwind in C++ compilations

from issue #52

librumprun_unwind -> libunwind

There's nothing rumprun-specific in there. The original idea with the
rumprun prefix was to avoid namespace conflicts, but if someone wants
to link in another libunwind we'll be in trouble regardless. Also,
consistency with libcompiler_rt.

Do not assume that all compiler invocations generate output.

Fixes a problem reported by Vincent Schwarzer, namely that
"ccwrapper -print-search-dirs" throws an error.

Specify C++ language standard and includes using compiler specs

To address issue #43, the gcc driver knows (based on a list of suffixes)
if it is compiling C or C++. So, we can use this knowledge in the specs
to set the required C++ standard.

Note that -std=c++11 must be specified in both the cpp_options and
cc1plus spec for this to work.

This change also sets the cpp options to only add the C++ include paths
when compiling C++ programs.

Default to -std=c++11

We do this here instead of in the specs file since I couldn't figure
out how to make -std=c++11 apply only to C++ for the preprocessor
options line. Fix if you know how.

The only bug is that "foo-gcc foo.cc" will not use C++11, but I'm
not sure we care about that.

No longer define the rumprun_fermented symbol.

The presense (or lack thereof) of the ELF note from which the baking
parameters are retrieved serves the same purpose.

Make rumpbake constant over all platforms.

Embed the necessary information to move from a ferment to a baked product
into an ELF note section. Use that information during baking to determine
where to find the appropriate toolchain from.

Display a verbose warning if RUMPRUN_STUBLINK is set.

Even if it's undocumented, people have a tendency to read the source.

cc.in: Allow overriding stub link failure

Add an undocumented RUMPRUN_STUBLINK toggle to always succeed in the
stub link phase, so that I can build clock_test with -DBMK without
having to modify the generated cc each time.

Build compiler wrapper as -gcc or -clang, not -cc.

Note: user-visible change (-cc was visible only for ~24h, so not
bothering with leaving -cc around as compat).

Rename the toolchain tuple to what was discussed on the mailing list.

e.g. x86_64-rumprun-netbsd will work now both for xen and hw. The
platform is selected during the "bake" phase, everything before that is
(or should be) platform-independent, only target ISA dependent.

Bake directly from rumpbake without calling compiler.

This decouples the compiler wrapper from any bake-time specs.

Don't give a generic LDFLAGS to app-tools, just LDFLAGS_BAKE

Apptools variable consistency naming.

Make everything that is a directory pathname contain "DIR"

Remove duplication from specs.

Call the compile/ferment one "compile-or-ferment". We need that
one to serve both roles, because "cc -o foo.c".

Remove the cpp/cc1 bits from the stub and bake "pure linker specs".

specs-inter -> specs-ferment

Follows change done for specs-final -> specs-bake.
Now the specfile names and the stage names are the same.

call the specs used by bake "specs-bake" instead of "specs-final"

honor LDFLAGS

if pseudolinking fails, cleanup the relocatable output

indent consistently with rest of rumpkernel.org

cc.in/rumpbake/rumprun: Don't depend on 'nm'

Make the magic symbols somewhat more magic and just use grep

cc.in: Cosmetic fix to use of -Wl,-u

cc.in: Don't need a temporary file here

Use standard idiom for switching on $0

rumprun: Refuse to run non-baked images

With the introduction of rumpbake, we don't want to confuse users who
will be following old instructions and running the output of
rumprun-*-cc directly.

Some build systems insist the intermediate output is executable

Rumpbake improvements

- Use TOOLCHAIN rather than CC in the configuration
- Embed a rumprun-specific symbol into the intermediate link output,
this is used by rumpbake to check that the user has passed a suitable
relocatable object. (And is also there as an example of how to embed
extra information about the output for later use by rumpbake.)

Fix C++ linkage

Introduce `rumpbake' for final linking of unikernels

As discussed on the mailing list:

- toolchain 'cc.in' produces an intermediate relocatable file, and
verifies the userspace link using a stub version of librumprun_base
and the minimal set of rump components.
- rumpbake is used to produce the final unikernel image, and supports
defining target configurations in rumpbake.conf.

use values from buildrump.sh toolchain-conf.mk

readability improvements

no functional change

run toolchain bits specified to buildrump.sh

platform-independence changes for app-tools

seed platform-independent app-tools with the platform/xen versions