fix: install LLVM via xlings before mcpp on Windows CI/release

xlings sandboxed binary has an upstream bug where large package
(LLVM 148MB) extraction fails on Windows — the download completes
but the payload doesn't appear at the expected xpkgs path.

Workaround: install LLVM via the system-level xlings before mcpp.
mcpp's package_fetcher finds it from the global xlings data dir.

The package_fetcher fallback (checking ~/.xlings/data/xpkgs/) handles
the case where xlings installs LLVM to its global dir instead of the
mcpp sandbox.

Author: Sunrisepeak

.github/workflows/ci-windows.yml

@@ -56,6 +56,10 @@ jobs:
           export PATH="$USERPROFILE/.xlings/subos/default/bin:$PATH"
           echo "$USERPROFILE/.xlings/subos/default/bin" >> "$GITHUB_PATH"
           xlings.exe --version
+          # Install LLVM first via system xlings — mcpp's sandboxed xlings
+          # has an upstream bug where large package extraction fails on Windows.
+          # See: https://github.com/mcpp-community/mcpp/pull/53
+          xlings.exe install llvm -y || xlings.exe install llvm@20.1.7 -y
           xlings.exe install mcpp -y
           echo "=== Searching for mcpp binary ==="
           find "$USERPROFILE/.xlings" -name "mcpp.exe" -o -name "mcpp" 2>/dev/null | head -10
@@ -75,24 +79,7 @@ jobs:
         run: |
           export MCPP_VENDORED_XLINGS="$XLINGS_BIN"
 
-          # Debug: check mcpp sandbox state before build
-          echo "=== mcpp self env ==="
-          "$MCPP" self env || true
-          echo "=== mcpp sandbox xlings binary ==="
-          SANDBOX_XLINGS="$USERPROFILE/.mcpp/registry/bin/xlings.exe"
-          if [ -f "$SANDBOX_XLINGS" ]; then
-            echo "exists: $SANDBOX_XLINGS"
-            XLINGS_HOME="$USERPROFILE/.mcpp/registry" "$SANDBOX_XLINGS" --version || true
-          else
-            echo "NOT FOUND: $SANDBOX_XLINGS"
-          fi
-
-          "$MCPP" build || {
-            echo "=== After failed build ==="
-            find "$USERPROFILE/.mcpp" -maxdepth 5 -name "xim-x-llvm" -type d 2>/dev/null
-            find "$USERPROFILE/.xlings" -maxdepth 5 -name "xim-x-llvm" -type d 2>/dev/null
-            exit 1
-          }
+          "$MCPP" build
 
           MCPP_SELF=$(find target -name "mcpp.exe" -path "*/bin/*" | head -1)
           test -n "$MCPP_SELF" || { echo "FAIL: no mcpp.exe"; exit 1; }

.github/workflows/release.yml

@@ -462,6 +462,7 @@ jobs:
           export PATH="$USERPROFILE/.xlings/subos/default/bin:$PATH"
           echo "$USERPROFILE/.xlings/subos/default/bin" >> "$GITHUB_PATH"
           xlings.exe --version
+          xlings.exe install llvm -y || xlings.exe install llvm@20.1.7 -y
           xlings.exe install mcpp -y
           MCPP=$(find "$USERPROFILE/.xlings" -name "mcpp.exe" -path "*/bin/*" 2>/dev/null | head -1)
           if [ -z "$MCPP" ]; then