nvidia-runtime: Set git user.name before applying patch (#198)

Should fix this:
```
Committer identity unknown

*** Please tell me who you are.

Run

  git config --global user.email "you@example.com"
  git config --global user.name "Your Name"

to set your account's default identity.
Omit --global to set the identity only in this repository.

fatal: empty ident name (for <runner@runnervmoqczp.1xlrnzp2busulcmx1tuvjmdqng.yx.internal.cloudapp.net>) not allowed
Error: Process completed with exit code 128.
```

Author: jepio

nvidia-runtime.sysext/create.sh

@@ -27,6 +27,8 @@ function populate_sysext_root() {
   git clone -b ${version} --depth 1 --recurse-submodules --shallow-submodules https://github.com/NVIDIA/nvidia-container-toolkit
   if [ "${version}" == v1.18.1 ]; then
     pushd nvidia-container-toolkit
+    git config --global user.name "github"
+    git config --global user.email "github@extensions.flatcar.org"
     git am "${scriptroot}/nvidia-runtime.sysext/0001-nvidia-runtime-1.18.1-go-dl.patch"
     git am "${scriptroot}/nvidia-runtime.sysext/0002-nvidia-runtime-1.18.1-submodule-update.patch"
     popd