download/git: more resilient in case of kill

In case the git backend gets killed right in-between it finished
initialising the repository, but before it could add the remote,
we'd end up with a repository without the 'origin' remote, so we
would not be able to change its URL.

Another case that may happen (like in the build failure, below),
is that the repository was initialised with a previous version
of Buildroot, before the commit e17719264b (download/git: don't
require too-recent git) was applied, and that trepository was
still lying around...

Fixes:
    http://autobuild.buildroot.org/results/25a/25aae054634368fadb265b97ebe4dda809deff6f/

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

support/download/git

@@ -47,13 +47,15 @@ git_cache="${dl_dir}/git"
 # fetch'ed later.
 if [ ! -d "${git_cache}" ]; then
     _git init "'${git_cache}'"
-    pushd "${git_cache}" >/dev/null
-    _git remote add origin "'${uri}'"
-    popd >/dev/null
 fi
 
 pushd "${git_cache}" >/dev/null
 
+# Ensure the repo has an origin (in case a previous run was killed).
+if ! git remote |grep -q -E '^origin$'; then
+    _git remote add origin "'${uri}'"
+fi
+
 _git remote set-url origin "'${uri}'"
 
 # Try to fetch with limited depth, since it is faster than a full clone - but