Android: fix git-pull, a symlink was required

git-pull.sh script should be linked to git-pull,
Also this script requires a tool named git-merge,
symlinked to main git binary.

+ Regroup all libcurl dependencies in a single bloc
+ Hide noisy sign warnings

Change-Id: I2ebd0dc52d0cca7336099130731e85a6e745cefd
Signed-off-by: Tanguy Pruvot <tanguy.pruvot@gmail.com>