vagrant: remove debian 9 "stretch" box

there are multiple issues with that box:
- debian 9 is out of support by debian, out of even lts support since 2022
- it has a OpenSSL 1.x natively (and our source based install also used 1.x) - that is also out of support and noone will care for it.

Also, borg2 will still take a while, so it would be
even more outdated at release time as it already
is now.

Vagrantfile

@@ -132,92 +132,6 @@ def packages_openindiana
   EOF
 end
 
-
-# Build and install borg dependencies from source
-def install_source_dependencies(user)
-  return <<-EOF
-    set -e -o pipefail
-
-    # Install in /usr/local
-    export PREFIX=/usr/local
-
-    # Make PKG_CONFIG_PATH explicit, even if /usr/local/lib/pkgconfig is enabled per default
-    export PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig
-    echo 'export PKG_CONFIG_PATH="'${PKG_CONFIG_PATH}'"' >> ~#{user}/.bash_profile
-
-    # All source packages integrate with pkg-config, remove any previous overrides
-    sed -i '/BORG_.*_PREFIX/d' ~#{user}/.bash_profile
-
-    # Setup pyenv to pick up the custom openssl version (python >= 3.9 requires openssl >= 1.1.1)
-    echo 'export PYTHON_CONFIGURE_OPTS="--with-openssl='"${PREFIX}"' --with-openssl-rpath=auto"' >> ~#{user}/.bash_profile
-    echo 'export LDFLAGS=-Wl,-rpath,'"${PREFIX}"'/lib' >> ~#{user}/.bash_profile
-
-    # Silence git warning about shallow clones
-    git config --global advice.detachedHead false
-
-    # libattr
-    VERSION_LIBATTR=2.5.1
-    curl -s -L https://download.savannah.nongnu.org/releases/attr/attr-${VERSION_LIBATTR}.tar.gz | tar xvz --strip-components=1 --one-top-level=attr -f - -C ${PREFIX}/src
-    cd ${PREFIX}/src/attr
-    ./configure --prefix=${PREFIX}
-    make -j$(nproc) install
-
-    # libacl
-    VERSION_LIBACL=2.3.1
-    curl -s -L https://download.savannah.nongnu.org/releases/acl/acl-${VERSION_LIBACL}.tar.gz | tar xvz --strip-components=1 --one-top-level=acl -f - -C ${PREFIX}/src
-    cd ${PREFIX}/src/acl
-    ./configure --prefix=${PREFIX}
-    make -j$(nproc) install
-
-    # liblz4
-    VERSION_LIBLZ4=1.9.4
-    git -C ${PREFIX}/src clone --depth 1 --branch v${VERSION_LIBLZ4} https://github.com/lz4/lz4.git
-    cd ${PREFIX}/src/lz4
-    make -j$(nproc) install PREFIX=${PREFIX}
-
-    # libzstd
-    VERSION_LIBZSTD=1.5.5
-    git -C ${PREFIX}/src clone --depth 1 --branch v${VERSION_LIBZSTD} https://github.com/facebook/zstd.git
-    cd ${PREFIX}/src/zstd
-    make -j$(nproc) install PREFIX=${PREFIX}
-
-    # xxHash
-    VERSION_LIBXXHASH=0.8.2
-    git -C ${PREFIX}/src clone --depth 1 --branch v${VERSION_LIBXXHASH} https://github.com/Cyan4973/xxHash.git
-    cd ${PREFIX}/src/xxHash
-    make -j$(nproc) install PREFIX=${PREFIX}
-
-    # openssl
-    VERSION_OPENSSL=1_1_1w
-    git -C ${PREFIX}/src clone --depth 1 --branch OpenSSL_${VERSION_OPENSSL} https://github.com/openssl/openssl.git
-    cd ${PREFIX}/src/openssl
-    ./config --prefix=${PREFIX} --openssldir=${PREFIX}/lib/ssl
-    make -j$(nproc)
-    make -j$(nproc) install
-
-    # libfuse3 requires ninja
-    VERSION_NINJA=1.11.1
-    git -C ${PREFIX}/src clone --depth 1 --branch v${VERSION_NINJA} https://github.com/ninja-build/ninja.git
-    cd ${PREFIX}/src/ninja
-    python3 configure.py --bootstrap
-    install --mode=755 --target-directory=${PREFIX}/bin ninja
-
-    # libfuse3 requires meson >= 0.50; python3.5 support is dropped in meson >= 0.57
-    VERSION_MESON=0.56.2
-    git -C ${PREFIX}/src clone --depth 1 --branch ${VERSION_MESON} https://github.com/mesonbuild/meson.git
-    ln -s ${PREFIX}/src/meson/meson.py ${PREFIX}/bin/meson
-
-    # libfuse3
-    VERSION_LIBFUSE=3.16.1
-    git -C ${PREFIX}/src clone --depth 1 --branch fuse-${VERSION_LIBFUSE} https://github.com/libfuse/libfuse.git
-    cd ${PREFIX}/src/libfuse
-    mkdir build; cd build
-    meson setup --prefix ${PREFIX} --libdir ${PREFIX}/lib ..
-    ninja
-    ninja install
-  EOF
-end
-
 def install_pyenv(boxname)
   return <<-EOF
     echo 'export PYTHON_CONFIGURE_OPTS="${PYTHON_CONFIGURE_OPTS} --enable-shared"' >> ~/.bash_profile
@@ -425,23 +339,6 @@ Vagrant.configure(2) do |config|
     b.vm.provision "run tests", :type => :shell, :privileged => false, :inline => run_tests("buster64", ".*none.*")
   end
 
-  config.vm.define "stretch64" do |b|
-    b.vm.box = "generic/debian9"
-    b.vm.provider :virtualbox do |v|
-      v.memory = 1024 + $wmem
-    end
-    b.vm.provision "fs init", :type => :shell, :inline => fs_init("vagrant")
-    b.vm.provision "packages debianoid", :type => :shell, :inline => packages_debianoid("vagrant")
-    b.vm.provision "install source dependencies", :type => :shell, :privileged => true, :inline => install_source_dependencies("vagrant")
-    b.vm.provision "install pyenv", :type => :shell, :privileged => false, :inline => install_pyenv("stretch64")
-    b.vm.provision "install pythons", :type => :shell, :privileged => false, :inline => install_pythons("stretch64")
-    b.vm.provision "build env", :type => :shell, :privileged => false, :inline => build_pyenv_venv("stretch64")
-    b.vm.provision "install borg", :type => :shell, :privileged => false, :inline => install_borg("llfuse")
-    b.vm.provision "install pyinstaller", :type => :shell, :privileged => false, :inline => install_pyinstaller()
-    b.vm.provision "build binary with pyinstaller", :type => :shell, :privileged => false, :inline => build_binary_with_pyinstaller("stretch64")
-    b.vm.provision "run tests", :type => :shell, :privileged => false, :inline => run_tests("stretch64", ".*none.*")
-  end
-
   config.vm.define "freebsd64" do |b|
     b.vm.box = "generic/freebsd14"
     b.vm.provider :virtualbox do |v|