Add README and workflow for 24.1 release branch

.github/workflows/mandrel.yml

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+name: Mandrel-Quarkus tests
+
+on:
+  push:
+    paths-ignore:
+      - '.github/workflows/main.yml'
+      - '.github/workflows/quarkus.yml'
+      - '**.md'
+  pull_request:
+    paths-ignore:
+      - '.github/workflows/main.yml'
+      - '.github/workflows/quarkus.yml'
+      - '**.md'
+  workflow_dispatch:
+
+# The following aims to reduce CI CPU cycles by:
+# 1. Cancelling any previous builds of this PR when pushing new changes to it
+# 2. Cancelling any previous builds of a branch when pushing new changes to it in a fork
+# 3. Cancelling any pending builds, but not active ones, when pushing to a branch in the main
+#    repository. This prevents us from constantly cancelling CI runs, while being able to skip
+#    intermediate builds. E.g., if we perform two pushes the first one will start a CI job and
+#    the second one will add another one to the queue; if we perform a third push while the
+#    first CI job is still running the previously queued CI job (for the second push) will be
+#    cancelled and a new CI job will be queued for the latest (third) push.
+concurrency:
+  group: "workflow = ${{ github.workflow }}, ref = ${{ github.event.ref }}, pr = ${{ github.event.pull_request.id }}"
+  cancel-in-progress: ${{ github.event_name == 'pull_request' || github.repository != 'graalvm/mandrel' }}
+
+jobs:
+  q-main-ea:
+    name: "Q main M 24.1 EA"
+    uses: graalvm/mandrel/.github/workflows/base.yml@default
+    with:
+      quarkus-version: "main"
+      repo: ${{ github.repository }}
+      version: ${{ github.ref }}
+      mandrel-packaging-version: "24.1"
+      jdk: "23/ea"
+  q-main-ea-win:
+    name: "Q main M 24.1 windows EA"
+    uses: graalvm/mandrel/.github/workflows/base-windows.yml@default
+    with:
+      quarkus-version: "main"
+      repo: ${{ github.repository }}
+      version: ${{ github.ref }}
+      mandrel-packaging-version: "24.1"
+      jdk: "23/ea"

README-Mandrel.md

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+# Mandrel
+
+Mandrel is [a downstream distribution of the GraalVM community edition](https://developers.redhat.com/blog/2020/06/05/mandrel-a-community-distribution-of-graalvm-for-the-red-hat-build-of-quarkus/).
+Mandrel's main goal is to provide a `native-image` release specifically to support [Quarkus](https://quarkus.io).
+The aim is to align the `native-image` capabilities from GraalVM with OpenJDK and Red Hat Enterprise Linux libraries to improve maintainability for native Quarkus applications.
+Mandrel can best be described as a distribution of a regular OpenJDK with a specially packaged GraalVM Native Image builder (`native-image`).
+
+## How Does Mandrel Differ From Graal
+
+Mandrel releases are built from a code base derived from the upstream GraalVM code base, with only minor changes but some significant exclusions. 
+A full distribution of GraalVM is much more than `native-image`: it has polyglot support, the Truffle framework which allows for efficient implementation of interpreters, an LLVM compiler back end for native image, the libgraal JIT compiler as a replacement for Hotspot’s C2 server compiler and much more.
+Mandrel is the small subset of that functionality we support for the `native-image` use-case.
+
+Mandrel's `native-image` also doesn't include the following features:
+* The experimental image-build server, i.e., the `--experimental-build-server` option.
+* The LLVM backend, i.e., the `-H:CompilerBackend=llvm` option.
+* The musl libc implementation, i.e., the `--libc=musl` option.
+* Support for generating static native images, i.e., the `--static` option.
+* Support for non JVM-based languages and polyglot, i.e., the `--language:<languageId>` option.
+
+Mandrel is also built slightly differently to GraalVM, using the standard OpenJDK project release of jdk17u.
+This means it does not profit from a few small enhancements that Oracle have added to the version of OpenJDK used to build their own GraalVM downloads.
+Most of these enhancements are to the JVMCI module that allows the Graal compiler to be run inside OpenJDK.
+The others are small cosmetic changes to behaviour.
+These enhancements may in some cases cause minor differences in the progress of native image generation.
+They should not cause the resulting images themselves to execute in a noticeably different manner.
+
+## Communication Channels
+
+* [Slack](https://www.graalvm.org/slack-invitation) - Join `#mandrel` channel at graalvm's slack workspace
+* [[email protected]](mailto:[email protected]?subject=[MANDREL]) mailing list - Subscribe [here](https://oss.oracle.com/mailman/listinfo/graalvm-dev)
+* [GitHub issues](https://github.com/graalvm/mandrel/issues) for bug reports, questions, or requests for enhancements.
+
+Please report security vulnerabilities according to the [Reporting Vulnerabilities guide](https://www.oracle.com/corporate/security-practices/assurance/vulnerability/reporting.html).
+
+## Getting Started
+
+Mandrel distributions can be downloaded from [the repository's releases](https://github.com/graalvm/mandrel/releases)
+and container images are available at [quay.io](https://quay.io/repository/quarkus/ubi-quarkus-mandrel-builder-image?tag=latest&tab=tags).
+
+### Prerequisites
+
+Mandrel's `native-image` depends on the following packages:
+* freetype-devel
+* gcc
+* glibc-devel
+* libstdc++-static
+* zlib-devel
+
+On Fedora/CentOS/RHEL they can be installed with:
+```bash
+dnf install glibc-devel zlib-devel gcc freetype-devel libstdc++-static
+```
+
+**Note**: The package might be called `glibc-static` or `libstdc++-devel` instead of `libstdc++-static` depending on your system.
+If the system is missing stdc++, `gcc-c++` package is needed too.
+
+On Ubuntu-like systems with:
+```bash
+apt install g++ zlib1g-dev libfreetype6-dev
+```
+
+## Building Mandrel From Source
+
+For building Mandrel from source please see [mandrel-packaging](https://github.com/graalvm/mandrel-packaging)
+and consult [Repository Structure in CONTRIBUTING.md](CONTRIBUTING.md#repository-structure) regarding which branch of Mandrel to use.
+
+# Community
+Empowering Software Development with Works on Arm Initiative
+![Works on Arm logo](img/works_on_arm_900x77.png)
+[Works on Arm](https://www.arm.com/solutions/infrastructure/works-on-arm) is a strategic initiative to enable and accelerate the
+software ecosystem for Arm64.
+
+[GraalVM's](https://www.graalvm.org/) [Mandrel](https://github.com/graalvm/mandrel) distribution that
+powers [Quarkus Native](https://quarkus.io/guides/building-native-image) proudly counts itself among the libraries and
+tools that successfully leveraged the resources from Works on Arm.