build-system/julia: Enable Julia Pkg to find installed packages.

build-system/julia: Enable Julia Pkg to find installed packages.

Julia's built-in package manager (Pkg) looks for packages in
JULIA_DEPOT_PATH/packages/PACKAGENAME/XXXX, where XXXX is a string
encoding package UUID and SHA1 of files.  The link-depot phase creates
a link at the correct location to allow Pkg to find packages that were
already installed by Guix.

* guix/build/julia-build-system.scm (link-depot): New phase.
(%package-path): Modified package path from packages/ to loadpath/.
(project.toml->uuid): New procedure, retrive package uuid from TOML file.
(precompile, check): Adjust to the change in paths.
(%standard-phases): Add link-depot phase.
(julia-build): Add julia-package-uuid keyword.
* guix/build-system/julia.scm (julia-build): Also use the
julia-package-uuid keyword.
* gnu/packages/julia-jll.scm (julia-bzip2-jll, julia-cairo-jll,
julia-compilersupportlibraries-jll, julia-expat-jll, julia-ffmpeg-jll,
julia-fontconfig-jll, julia-freetype2-jll, julia-fribidi-jll,
julia-gettext-jll, julia-glib-jll, julia-gr-jll, julia-gumbo-jll,
julia-imagemagick-jll, julia-jllwrappers-jll, julia-jpegturbo-jll,
julia-lame-jll, julia-libass-jll, julia-libfdk-aac-jll,
julia-libffi-jll, julia-libgcrypt-jll, julia-libglvnd-jll,
julia-libgpg-error-jll, juli-libiconv-jll, julia-libmount-jll,
julia-libpng-jll, julia-libsass-jll, julia-libtiff-jll,
julia-libuuid-jll, julia-libvorbis-jll, julia-lzo-jll,
julia-mbedtls-jll, julia-ogg-jll, julia-openspecfun-jll,
julia-openssl-jll, julia-opus-jll, julia-pcre-jll, julia-pixman-jll,
julia-qt5base-jll, julia-wayland-jll, julia-wayland-protocols-jll,
julia-x264-jll, julia-x265-jll, julia-xkbcommon-jll, julia-xml2-jll,
julia-xorg-libpthread-stubs-jll, julia-xorg-libx11-jll,
julia-xorg-libxau-jll, julia-xorg-libxcb-jll, julia-xorg-libxcursor-jll,
julia-xorg-libxdmcp-jll, julia-xorg-libxext-jll,
julia-xorg-libxfixes-jll, julia-xorg-libxi-jll,
julia-xorg-libxinerama-jll, julia-xorg-libxkbfile-jll,
julia-xorg-libxrandr-jll, julia-xorg-libxrender-jll,
julia-xorg-xcb-util-jll, julia-xorg-xcb-util-keysyms-jll,
julia-xorg-xcb-util-renderutil-jll, julia-xorg-xcb-util-wm-jll,
julia-xorg-xkbcomp-jll, julia-xorg-xkeyboard-config-jll,
julia-xorg-xtrans-jll, julia-xslt-jll, julia-zlib-jll, julia-zstd-jll)
[argument]: Adjust the order of the phases to the change in the
julia-build-system.
* gnu/packages/julia-xyz.scm (julia-bufferedstreams, julia-calculus,
julia-dataframes, julia-datavalues, julia-distances, julia-documenter,
julia-dualnumbers, julia-ellipsisnotation, julia-expronicon,
julia-fileio, julia-fixedpointnumbers, julia-functionwrappers,
julia-fuzzycompletions, julia-genericlinearalgebra, julia-genericschur,
julia-geometrybasics, julia-imagemagick, julia-infinity,
julia-matrixfactorizations, julia-media, julia-missings, julia-nnlib,
julia-optimtestproblems, julia-orderedcollections, julia-prettytables,
julia-pycall, julia-quadmath, julia-safetests, julia-stackviews)
[arguments]: Correct paths to reflect change of %package-path modify
order of phases as link-depot needs to run on an unmodified src
directory add package-name-uuid keyword argument to packages without
Project.toml file.
* gnu/packages/julia.scm (julia)[native-search-paths]: Correct paths to
reflect change of %package-path modify order of phases as link-depot
needs to run on an unmodified src directory.

Signed-off-by: Efraim Flashner <efraim@flashner.co.il>