ci: add a workflow to test if the Vinix kernel builds (#10963)

.github/workflows/vinix-kernel.yml

@@ -0,0 +1,29 @@
+name: Build Vinix kernel
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install dependencies
+        run: sudo apt-get update && sudo apt-get install build-essential meson -y
+      - name: Build V
+        run: make
+      - name: Clone current Vinix
+        run: git clone https://github.com/vlang/vinix.git --depth=1
+      - name: Clone current mlibc
+        run: git clone https://github.com/managarm/mlibc.git --depth=1
+      - name: Patch mlibc for Vinix
+        run: cd mlibc && patch -p3 < ../vinix/patches/mlibc/mlibc.patch
+      - name: Install mlibc headers
+        run: mkdir mlibc-build && cd mlibc-build && meson --cross-file ../vinix/cross_file.txt --prefix=/ -Dheaders_only=true ../mlibc && ninja && mkdir ../mlibc-headers && DESTDIR=`realpath ../mlibc-headers` ninja install
+      - name: Attempt to build the Vinix kernel (debug)
+        run: cd vinix/kernel && make PROD=false CFLAGS="-O2 -g -pipe -I../mlibc-headers" V="../../v" && make clean
+      - name: Attempt to build the Vinix kernel (prod)
+        run: cd vinix/kernel && make PROD=true CFLAGS="-O2 -g -pipe -I../mlibc-headers" V="../../v" && make clean