[Misc] Use https as the default git protocol

Summary:
- Use https for github repo URL
- Add executable permission to configure

Test Plan:

Reviewed-by: luchsh

Issue: https://github.com/alibaba/dragonwell8/issues/20

get_source_dragonwell.sh

@@ -63,7 +63,7 @@ do
       shift;
       site=$1
       if [[ $site == "github" ]]; then
-        GITURL="git@github.com:alibaba"
+        GITURL="https://github.com/alibaba"
         REPO_PREFIX="dragonwell8_"
       elif [[ $site == "gitlab" ]]; then
         # inside alibaba