Guix,

The 'core-updates' branch is ready for testing!  This is a very early
stage, so many substitutes are missing.  Consider yourself warned ;-)

I have compiled a summary of the changes below.  The package updates are
too numerous to list here; try `git shortlog -n master..core-updates`
for the scoop.

We are still waiting for armhf to catch up on the CI, as well as
<https://issues.guix.info/issue/36535> before starting the full
rebuild.  I will send another email when that happens, along with a
status update.

* Build system changes
** 'python-build-system' runs tests after installing the package,
   instead of in between the 'build' and 'install' phases, to improve
   reproducibility.
** 'python-build-system' does not wrap already-wrapped executables.
** 'python-build-system' has a (python-version ...) procedure that
   returns the major+minor version of a given python package.
** 'meson-build-system' produces optimized binaries with debugging
   symbols by default, similar to 'cmake-build-system'.
** 'meson-build-system' no longer attempts to run Autotools bootstrap
   scripts.
** 'gnu-build-system' (and those inheriting from it) has deterministic
   behavior in some corner cases (<https://issues.guix.info/35387).
** gnu-build-system copies license files to all outputs instead of just
   "out".  It now also works for out-of-source builds.
** (guix build utils) has a new 'wrap-script' procedure that replaces
   the shebang in scripts in a language-aware manner, as an alternative
   to the shell wrapper created by 'wrap-program'.
** (invoke ...) from the same module now reports errors in a
   human-friendly way, instead displaying a long stack trace.
** There is also a new (invoke/quiet ...) that swallows program output,
   unless it fails.  The return value is unspecified.

* Toolchain changes
** On i686 and x86_64, the "binary seeds" at the root of the dependency
   graph no longer includes GCC, glibc, and binutils.  Instead they are
   built from source using a new GNU Mes based toolchain, reducing the
   set of trusted bootstrap binaries from ~250MiB to ~130MiB.
** GCC 7 became the default compiler.  Consequently, C_INCLUDE_PATH and
   CPLUS_INCLUDE_PATH are no longer set in the build environment.
   Packages that rely on those variables or their CROSS_ counterparts
   will need to be adjusted to use {CROSS_,}CPATH instead.
** GNU/Hurd no longer uses a special glibc variant.
** Guile was updated to 2.2.6, and libgc to 7.6.12.
** Linux-Libre headers was updated to 4.19.57.
** Glibc was updated to 2.29.
** Binutils was updated to 2.32.
** coreutils was updated to 8.31.
** Bash was updated to 5.0.7.
** Grep 3.3, Gawk 5.0.1, Gettext 0.20.1, diffutils 3.7, Bison 3.4.1, ...

Other noteworthy changes:
** GNOME was updated to 3.30.
** OpenSSL 1.1.1 is the default 'openssl' package.
** Many packages were migrated to use Python 3 instead of Python 2.
** cURL and GNU SASL use MIT Kerberos instead of GNU Security Services.
** Python 2 builds reproducibly.
** Python (2 & 3) no longer uses a bundled copy of Expat.
** CMake was updated 3.14.5.
** CMake comes with documentation, too.
** Perl was updated to 5.30.0.
** Python was updated to 3.7.4.
** Boost was updated to 1.70.0.
** SQLite was updated to 3.28.0.
** Pytest was updated to 4.4.2.