Allow different repo urls in bootstrap.sh for dev

Having to clone from github or a remote repository in general during
development is a waste of bandwidth, time and does not work during
development while a change is being tested and not yet commited or
pushed. Now remote urls can be configured through two env variables:
MACOS_SYSTEM_REPO_URL and ZSHLIB_REPO_URL.

bootstrap.sh

@@ -1,10 +1,23 @@
 #!/usr/bin/env zsh
 
+function cloneMacOSSystemRepo() {
+  local repoUrl="${MACOS_SYSTEM_REPO_URL:-https://github.com/astzweig/macos-system.git}"
+  git clone -q "${repoUrl}" .
+}
+
+function cloneZSHLibRepo() {
+  local zshlibRepoUrl="${ZSHLIB_REPO_URL:-https://github.com/astzweig/zshlib.git}"
+  git config --file=.gitmodules submodule.zshlib.url "${zshlibRepoUrl}"
+  git submodule -q sync
+  git submodule -q update --init --recursive --remote
+}
+
 function main() {
   local tmddir="`mktemp -d -t 'macos-system'`"
   trap 'rm -fr -- "${tmpdir}"' EXIT
   pushd -q "${tmddir}"
-  git clone -q --recurse-submodules https://github.com/astzweig/macos-system.git .
+  cloneMacOSSystemRepo
+  cloneZSHLibRepo
   ./install.sh
   popd -q
 }