feat(library): Introduce Lua

Introduce Lua 5.4.4 native application for Unikraft.

Add required files: `Kraftfile`, `Makefile.uk` and `README.md`.

The root filesystem (in `rootfs/`) provides the `helloworld.lua` file,
passed to as the `cmd` in `Kraftfile`.

Signed-off-by: Razvan Deaconescu <[email protected]>

.github/workflows/library-lua5.4.yaml

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+name: library/lua5.4
+
+on:
+  schedule:
+  - cron: '0 0 * * *' # Everyday at 12AM
+
+  push:
+    branches: [main]
+    paths:
+    - 'library/lua5.4/**'
+    - '.github/workflows/library-lua5.4.yaml'
+
+  pull_request:
+    types: [opened, synchronize, reopened]
+    branches: [main]
+    paths:
+    - 'library/lua5.4/**'
+    - '.github/workflows/library-lua5.4.yaml'
+
+jobs:
+  build:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+        - plat: qemu
+          arch: x86_64
+        - plat: qemu
+          arch: arm64
+        - plat: fc
+          arch: x86_64
+        - plat: fc
+          arch: arm64
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Build lua5.4
+      uses: unikraft/kraftkit@staging
+      with:
+        loglevel: debug
+        workdir: library/lua5.4
+        runtimedir: /github/workspace/.kraftkit
+        plat: ${{ matrix.plat }}
+        arch: ${{ matrix.arch }}
+        push: false
+        output: oci://index.unikraft.io/unikraft.org/lua:5.4
+
+    - name: Archive OCI digests
+      uses: actions/upload-artifact@v3
+      with:
+        name: oci-digests-${{ matrix.arch }}-${{ matrix.plat }}
+        path: ${{ github.workspace }}/.kraftkit/oci/digests
+        if-no-files-found: error
+
+  push:
+    if: ${{ github.event_name == 'push' || github.event_name == 'schedule' }}
+    needs: [ build ]
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Login to OCI registry
+      uses: docker/login-action@v2
+      with:
+        registry: index.unikraft.io
+        username: ${{ secrets.REG_USERNAME }}
+        password: ${{ secrets.REG_TOKEN }}
+
+    - name: Retrieve, merge and push OCI digests
+      uses: ./.github/actions/merge-oci-digests
+      with:
+        name: index.unikraft.io/unikraft.org/lua:5.4
+        push: true

library/lua/Kraftfile

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+spec: v0.6
+
+name: lua
+
+rootfs: ./rootfs
+
+cmd: ["/helloworld.lua"]
+
+unikraft:
+  version: stable
+  kconfig:
+    CONFIG_LIBRAMFS: 'y'
+    CONFIG_LIBUK9P: 'y'
+    CONFIG_LIBUKBUS: 'y'
+    CONFIG_LIBUKCPIO: 'y'
+    CONFIG_LIBUKDEBUG_ANSI_COLOR: 'y'
+    CONFIG_LIBUKLIBPARAM: 'y'
+    CONFIG_LIBVFSCORE_AUTOMOUNT_ROOTFS: 'y'
+    CONFIG_LIBVFSCORE_FSTAB: 'y'
+    CONFIG_LIBVFSCORE_ROOTFS_INITRD: 'y'
+
+targets:
+- qemu/x86_64
+- qemu/arm64
+- fc/x86_64
+- fc/arm64
+
+libraries:
+  musl: stable
+  lua:
+    version: stable
+    kconfig:
+      CONFIG_LUA_MAIN_FUNCTION: 'y'

library/lua/Makefile.uk

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+$(eval $(call addlib,applua))

library/lua/README.md

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+# Lua 5.4 Image
+
+This directory contains the definition for the `unikraft.org/lua:5.4` image.
+
+To run this image, [install Unikraft's companion command-line toolchain `kraft`](https://unikraft.org/docs/cli) and then you can run:
+
+```
+kraft run unikraft.org/lua:5.4
+```
+
+Once executed you will get a "Hello, World!" message.
+
+## See also
+
+- [How to run unikernels locally in Unikraft's Documentation](https://unikraft.org/docs/cli/running).

library/lua/rootfs/helloworld.lua

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+print("Hello, World!")