toolchain: switch to a two stage gcc build

Currently, the internal toolchain backend does a three stage gcc
build, with the following sequence of builds:

 - build gcc-initial
 - configure libc, install headers and start files
 - build gcc-intermediate
 - build libc
 - build gcc-final

However, it turns out that this is not necessary, and only a two stage
gcc build is needed. At some point, it was believed that a three stage
gcc build was needed for NPTL based toolchains with old gcc versions,
but even a gcc 4.4 build with a NPTL toolchain works fine.

So, this commit switches the internal toolchain backend to use a two
stage gcc build: just gcc-initial and gcc-final. It does so by:

 * Removing the custom dependency of all C libraries build step to
   host-gcc-intermediate. Now the C library packages simply have to
   depend on host-gcc-initial as a normal dependency (which they
   already do), and that's it.

 * Build and install both gcc *and* libgcc in
   host-gcc-initial. Previously, only gcc was built and installed in
   host-gcc-initial. libgcc was only done in host-gcc-intermediate,
   but now we need libgcc to build the C library.

 * Pass appropriate environment variables to get SSP (Stack Smashing
   Protection) to work properly:

    - Tell the compiler that the libc will provide the SSP support, by
      passing gcc_cv_libc_provides_ssp=yes. In Buildroot, we have
      chosen to use the SSP support from the C library instead of the
      SSP support from the compiler (this is not changed by this patch
      series, it was already the case).

    - Tell glibc to *not* build its own programs with SSP support. The
      issue is that if glibc detects that the compiler supports
      -fstack-protector, then glibc uses it to build a few things with
      SSP. However, at this point, the support is not complete (we
      only have host-gcc-initial, and the C library is not completely
      built). So, we pass libc_cv_ssp=no to tell the C library to not
      use SSP support itself. Note that this is not a big loss: only a
      few parts of the C library were built with -fstack-protector,
      not the entire library.

 * A special change is needed for ARC, because its libgcc depends on
   the C library, which breaks building libgcc in
   host-gcc-initial. This looks like a bug in the ARC compiler, as it
   does not obey the inhibit_libc variable which tells the compiler
   build process to *not* enable things that depend on the C
   library. So for now, in host-gcc-initial, we simply disable the
   build of libgmon.a for ARC. It's going to be built as part of
   host-gcc-final, so the final compiler will have gmon support.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
gcc/gcc-intermediate: remove package

Now that we have switched to a two steps gcc build process that uses
only gcc-initial and gcc-final, we can get rid of the gcc-intermediate
package.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
musl: two-stage gcc simplifications

After switching to a two stage gcc solution, there is no longer a need
to do weird things in the musl build, with certain things being done
twice (MUSL_CONFIGURE_CALL). Now the MUSL_CONFIGURE_CMDS variable only
does the configuration, and the MUSL_BUILD_CMDS only does the build,
as it should be.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
glibc: two-stage gcc simplifications

After switching to a two stage gcc solution, there is no longer a need
to do weird things in the glibc build. We can greatly simplify
GLIBC_CONFIGURE_CMDS to only do the configuration, and let the
existing GLIBC_BUILD_CMDS do the build.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
uclibc: two-stage gcc simplifications

After switching to a two stage gcc solution, there is no longer a need
to do weird things in the uclibc build. We can greatly simplify
UCLIBC_CONFIGURE_CMDS to only do the configuration, and let the
existing UCLIBC_BUILD_CMDS do the build. Note that we have to build
the headers before starting the C library build, otherwise there is a
build failure (probably a uClibc bug).

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
skeleton: remove symlinks from /var/log and /var/spool
Makefile: update version string
Add README.md
skeleton: add sysctl.conf
Add mksdcard script
Add busybox.config
Add raspi-kernel.config
Add raspi-kernel.patch
skeleton: update /etc/fstab
rpi-firmware: bump version
skeleton: add init.d helper script
openssh: update init.d script
openssh: use /etc/ssh as conf dir
git: bump version to 2.0.2
hostapd: install sysv script and sample conf file