provisioning: remove external-only downloads and git-clones

coin/provisioning/common/linux/install-cpdb.sh:git clone -q "$gitUrl" # gitUrl="https://github.com/openprinting/cpdb-libs.git"

coin/provisioning/common/linux/install-flite.sh:git clone -q "$gitUrl" # gitUrl="https://github.com/festvox/flite.git"

coin/provisioning/common/linux/install-vcpkg.sh:git clone "$vcpkgRepo" "$vcpkgRoot"

coin/provisioning/common/unix/emsdk.sh: sudo git clone https://github.com/emscripten-core/emsdk.git

coin/provisioning/common/unix/install-breakpad.sh: git clone https://chromium.googlesource.com/breakpad/breakpad "$breakpadHome"

coin/provisioning/common/unix/install-breakpad.sh: git clone https://chromium.googlesource.com/linux-syscall-support "$breakpadHome/src/third_party/lss"

coin/provisioning/common/windows/emsdk.ps1: C:\PROGRA~1\Git\bin\git clone https://github.com/emscripten-core/emsdk.git

coin/provisioning/common/windows/install-breakpad.ps1: git.exe clone "https://chromium.googlesource.com/breakpad/breakpad"

coin/provisioning/common/windows/install-breakpad.ps1: git.exe clone "https://chromium.googlesource.com/linux-syscall-support breakpad\third_party\ssl"

coin/provisioning/qtci-linux-Ubuntu-18.04-x86_64/02-git_lfs.sh:curl -L https://packagecloud.io/github/git-lfs/gpgkey | sudo apt-key add -
coin/provisioning/qtci-linux-Ubuntu-18.04-x86_64/02-git_lfs.sh-sudo apt-add-repository 'deb https://packagecloud.io/github/git-lfs/ubuntu/ xenial main'
coin/provisioning/qtci-linux-Ubuntu-18.04-x86_64/02-git_lfs.sh-sudo apt update
coin/provisioning/qtci-linux-Ubuntu-18.04-x86_64/02-git_lfs.sh-sudo apt install git-lfs
(found in other Ubuntus too)