fix: wrap scan-deps in cmd /c for shell redirect + 7z for release LLVM

ninja on Windows uses CreateProcess which doesn't interpret `>`
as shell redirection. Wrap the clang-scan-deps command in `cmd /c`
so stdout redirect to $out works correctly.

Also update release.yml to use 7z for LLVM extraction.

Author: Sunrisepeak

.github/workflows/release.yml

@@ -484,11 +484,16 @@ jobs:
           LLVM_VER="20.1.7"
           LLVM_DEST="$USERPROFILE/.mcpp/registry/data/xpkgs/xim-x-llvm/$LLVM_VER"
           if [ ! -f "$LLVM_DEST/bin/clang++.exe" ]; then
-            curl -fsSL -o /tmp/llvm.tar.xz \
+            WORK=$(mktemp -d)
+            curl -fSL --retry 3 -o "$WORK/llvm.tar.xz" \
               "https://github.com/xlings-res/llvm/releases/download/$LLVM_VER/llvm-$LLVM_VER-windows-x86_64.tar.xz"
             mkdir -p "$LLVM_DEST"
-            tar -xf /tmp/llvm.tar.xz -C "$LLVM_DEST" --strip-components=1
-            rm -f /tmp/llvm.tar.xz
+            cd "$WORK"
+            7z x -y llvm.tar.xz && 7z x -y llvm.tar -o"$LLVM_DEST" -aoa
+            INNER=$(ls -d "$LLVM_DEST"/llvm-* 2>/dev/null | head -1)
+            [ -d "$INNER/bin" ] && mv "$INNER"/* "$LLVM_DEST"/ && rmdir "$INNER" 2>/dev/null || true
+            cd -
+            rm -rf "$WORK"
           fi
 
           "$MCPP" build

src/build/ninja_backend.cppm

@@ -317,8 +317,10 @@ std::string emit_ninja_string(const BuildPlan& plan) {
         } else {
             // Clang path: clang-scan-deps produces P1689 JSON to stdout.
 #if defined(_WIN32)
-            append("  command = $scan_deps -format=p1689 -- "
-                   "$cxx $cxxflags -c $in -o $compile_target > $out\n");
+            // Wrap in cmd /c for shell redirection (ninja on Windows uses
+            // CreateProcess which doesn't interpret > as redirect).
+            append("  command = cmd /c \"$scan_deps -format=p1689 -- "
+                   "$cxx $cxxflags -c $in -o $compile_target > $out\"\n");
 #else
             append("  command = $toolenv $scan_deps -format=p1689 -- "
                    "$cxx $cxxflags -c $in -o $compile_target > $out\n");