build: Add Windows cross-compilation support from Linux using MSYS2 and WINE

.github/workflows/hydrun.yaml

@@ -18,6 +18,12 @@ jobs:
             flags: -e '--privileged'
             cmd: ./Hydrunfile
             dst: out/*
+          - id: stfs-windows
+            src: .
+            os: fedora:35
+            flags: -e '--privileged'
+            cmd: ./Hydrunfile windows
+            dst: out/*
 
     steps:
       - name: Maximize build space

Hydrunfile

@@ -2,6 +2,38 @@
 
 set -e
 
+# Windows
+if [ "$1" = "windows" ]; then
+    # Install native dependencies
+    dnf update -y
+    dnf install -y curl wine
+
+    # Install MSYS2
+    curl -L -o /tmp/msys2.exe 'https://github.com/msys2/msys2-installer/releases/download/2021-11-30/msys2-base-x86_64-20211130.sfx.exe'
+    wine64 /tmp/msys2.exe x -y -oC:/
+
+    # Fix MSYS2 TLS
+    sed -i ~/.wine/drive_c/msys64/etc/pacman.conf -e 's/SigLevel    = Required/SigLevel = Never/g'
+    cat /etc/pki/tls/certs/ca-bundle.crt >~/.wine/drive_c/msys64/usr/ssl/certs/ca-bundle.crt
+    cat /etc/pki/tls/certs/ca-bundle.trust.crt >~/.wine/drive_c/msys64/usr/ssl/certs/ca-bundle.trust.crt
+
+    # Install GCC and Go
+    export WINEPATH='c:\msys64\usr\bin'
+    wine64 bash.exe -c 'pacman --verbose --debug --noconfirm --ignore pacman --needed -S base-devel mingw-w64-x86_64-gcc mingw-w64-x86_64-go'
+
+    # Copy source code to directory on C drive
+    mkdir -p ~/.wine/drive_c/users/root/Documents/stfs
+    cp -rf . ~/.wine/drive_c/users/root/Documents/stfs
+    mkdir -p ~/.wine/drive_c/users/root/go
+
+    wine64 bash.exe -c 'export PATH="$PATH:/mingw64/bin" && cd /c/users/root/Documents/stfs && export GOPATH="/c/users/root/go" && export GOROOT="/mingw64/lib/go" && go build -o out/stfs.windows-x86_64 ./cmd/stfs'
+
+    mkdir -p out
+    cp -f ~/.wine/drive_c/users/root/Documents/stfs/out/* out
+
+    exit 0
+fi
+
 # Install native dependencies
 apt update
 apt install -y curl