Dockerfile.linux: backup mirrors for external gits (savannah.gnu)

[plowsof]

temp offline:

fatal: unable to access 'https://git.savannah.gnu.org/git/freetype/freetype2.git/': Failed to connect to git.savannah.gnu.org port 443: Connection timed out

monero-gui/Dockerfile.linux

Line 124 in 08e2eaf

RUN git clone -b VER-2-10-2 --depth 1 https://git.savannah.gnu.org/git/freetype/freetype2.git && \

mirror @ https://github.com/aseprite/freetype2 but no branch VER 2-10-2 only 2-10-0

im looking at improving the Dockerfile.linux build environment for GUI. main things so far:

• removal of apt with debs downloaded manually.
  • list of backup deb mirrors are supported
  • built in an offline container

these debs are no longer installed/required in the build environment:

build-essential_12.1ubuntu2_amd64.deb
fakeroot_1.20.2-1ubuntu1_amd64.deb
ifupdown_0.8.10ubuntu1.4_amd64.deb
iproute2_4.3.0-1ubuntu3.16.04.5_amd64.deb
isc-dhcp-client_4.3.3-5ubuntu12.10_amd64.deb
isc-dhcp-common_4.3.3-5ubuntu12.10_amd64.deb
krb5-locales_1.13.2+dfsg-5ubuntu2.2_all.deb
less_481-2.1ubuntu0.2_amd64.deb
libalgorithm-diff-perl_1.19.03-1_all.deb
libalgorithm-diff-xs-perl_0.04-4build1_amd64.deb
libalgorithm-merge-perl_0.08-3_all.deb
libasprintf-dev_0.19.7-2ubuntu3.1_amd64.deb
libatm1_2.5.1-1.5_amd64.deb
libdns-export162_9.10.3.dfsg.P4-8ubuntu1.19_amd64.deb
libfakeroot_1.20.2-1ubuntu1_amd64.deb
libfile-fcntllock-perl_0.22-3_amd64.deb
libgettextpo-dev_0.19.7-2ubuntu3.1_amd64.deb
libgettextpo0_0.19.7-2ubuntu3.1_amd64.deb
libisc-export160_9.10.3.dfsg.P4-8ubuntu1.19_amd64.deb
libltdl-dev_2.4.6-0.1_amd64.deb
libltdl7_2.4.6-0.1_amd64.deb
libmnl0_1.0.3-5_amd64.deb
libpopt0_1.16-10_amd64.deb
libsasl2-modules_2.1.26.dfsg1-14ubuntu0.2_amd64.deb
libtxc-dxtn-s2tc0_0~git20131104-1.1_amd64.deb
libusb-1.0-doc_1.0.20-1_all.deb
libx11-doc_1.6.3-1ubuntu2.2_all.deb
libxmuu1_1.1.2-2_amd64.deb
libxtables11_1.6.0-2ubuntu3_amd64.deb
manpages-dev_4.04-2_all.deb
manpages_4.04-2_all.deb
netbase_5.3_all.deb
openssh-client_7.2p2-4ubuntu2.10_amd64.deb
rename_0.20-4_all.deb
rsync_3.1.1-3ubuntu1.3_amd64.deb
sgml-base_1.26+nmu4ubuntu1_all.deb
shared-mime-info_1.5-2ubuntu0.2_amd64.deb
wget_1.17.1-1ubuntu1.5_amd64.deb
xauth_1.0.9-1ubuntu2_amd64.deb
xdg-user-dirs_0.15-2ubuntu6.16.04.1_amd64.deb
xml-core_0.13+nmu2_all.deb

I plan to use these tarballs (ht, no mirrors supported yet, nor found, so i could provide http mirror for them todo.
infact im not even sure i can prove that these hashes are real/verified / todo.

tarball_list=(
    "http://sources.buildroot.net/expat/expat-2.4.8.tar.xz" "0584a7318a4c007f7ec94778799d72fe"
    "http://sources.buildroot.net/boost/boost_1_80_0.tar.bz2" "df7dc2fc6de751753198a5bf70210da7"
    "http://sources.buildroot.net/libopenssl/openssl-1.1.1u.tar.gz" "72f7ba7395f0f0652783ba1089aa0dcc"
    "http://sources.buildroot.net/unbound/unbound-1.16.2.tar.gz" "974cbd17e2e2373f36bfce0ad5b1d4a1"
)

and now backup mirrors the the external repos would be needed to make things less fragile.
http://guigit.monerodevs.org:3000/explore/repos ✔️ ^