Dockerfile: update rootlesskit to v1.1.1, and use tags as reference

Commit 0b1c1877c5285fc78c0faa35a040e255d46a40a6 updated the version in
hack/dockerfile/install/rootlesskit.installer, but forgot to update the
version in Dockerfile.

Also updating both to use a tag, instead of commit. While it's good to pin by
an immutable reference, I think it's reasonably safe to use the tag, which is
easier to use, and what we do for other binaries, such as runc as well.

Full diff: https://github.com/rootless-containers/rootlesskit/compare/v1.1.0...v1.1.1

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit e27ffdab0f883034507272645e1f226886717224)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Dockerfile

@@ -344,8 +344,8 @@ FROM tini-${TARGETOS} AS tini
 FROM base AS rootlesskit-src
 WORKDIR /usr/src/rootlesskit
 RUN git init . && git remote add origin "https://github.com/rootless-containers/rootlesskit.git"
-# When updating, also update rootlesskit commit in vendor.mod accordingly.
-ARG ROOTLESSKIT_VERSION=v1.1.0
+# When updating, also update vendor.mod and hack/dockerfile/install/rootlesskit.installer accordingly.
+ARG ROOTLESSKIT_VERSION=v1.1.1
 RUN git fetch -q --depth 1 origin "${ROOTLESSKIT_VERSION}" +refs/tags/*:refs/tags/* && git checkout -q FETCH_HEAD
 
 FROM base AS rootlesskit-build

hack/dockerfile/install/rootlesskit.installer

@@ -1,8 +1,7 @@
 #!/bin/sh
 
-# When updating, also update rootlesskit commit in vendor.mod accordingly
-# v1.1.1
-: "${ROOTLESSKIT_VERSION:=a2c596ff9b3fddc0c2becb38f2ef4004f15765b5}"
+# When updating, also update vendor.mod and Dockerfile accordingly.
+: "${ROOTLESSKIT_VERSION:=v1.1.1}"
 
 install_rootlesskit() {
 	case "$1" in