refactor: use xlings install mcpp@0.0.16 for macOS self-host builds

Now that mcpp@0.0.16 is in xlings-res with the libc++ fix,
CI and release workflows can simply:
  xlings install mcpp → mcpp build

No xmake needed — mcpp self-hosts on macOS via xlings ecosystem.

Author: Sunrisepeak

.github/workflows/ci-macos.yml

@@ -268,35 +268,15 @@ jobs:
             *)              echo "FAIL: unexpected platform"; exit 1 ;;
           esac
 
-      - name: Build mcpp from source (xmake)
+      - name: Install mcpp@0.0.16 via xlings
         run: |
-          brew install xmake
-          # Temporary xmake.lua — not committed to repo
-          cat > /tmp/xmake_bootstrap.lua << 'EOF'
-          add_rules("mode.release")
-          set_languages("c++23")
-          package("cmdline")
-              set_homepage("https://github.com/mcpplibs/cmdline")
-              add_urls("https://github.com/mcpplibs/cmdline/archive/refs/tags/$(version).tar.gz")
-              add_versions("0.0.1", "3fb2f5495c1a144485b3cbb2e43e27059151633460f702af0f3851cbff387ef0")
-              on_install(function (package)
-                  import("package.tools.xmake").install(package)
-              end)
-          package_end()
-          add_requires("cmdline 0.0.1")
-          target("mcpp")
-              set_kind("binary")
-              add_files("src/main.cpp")
-              add_files("src/**.cppm")
-              add_packages("cmdline")
-              add_includedirs("src/libs/json")
-              set_policy("build.c++.modules", true)
-          EOF
-          cp /tmp/xmake_bootstrap.lua xmake.lua
-          xmake f -y -m release --toolchain=llvm --sdk="$LLVM_ROOT"
-          xmake build -y mcpp
-          rm -f xmake.lua
-          MCPP=$(find build -name mcpp -type f -perm +111 | head -1)
-          test -x "$MCPP"
-          "$MCPP" --version
-          echo ":: Build successful!"
+          xlings install mcpp -y
+          mcpp --version
+
+      - name: Self-host (mcpp builds mcpp)
+        run: |
+          mcpp build
+          SELFHOST=$(find target -path "*/bin/mcpp" | head -1)
+          test -x "$SELFHOST"
+          "$SELFHOST" --version
+          echo ":: Self-host successful!"

.github/workflows/release.yml

@@ -315,33 +315,17 @@ jobs:
           LLVM_ROOT=$(find "$HOME/.xlings" -path "*/xpkgs/xim-x-llvm/*/bin/clang++" | head -1 | xargs dirname | xargs dirname)
           echo "LLVM_ROOT=$LLVM_ROOT" >> "$GITHUB_ENV"
 
-      - name: Build mcpp (xmake + LLVM)
+      - name: Install mcpp@0.0.16 via xlings
         run: |
-          brew install xmake
-          cat > xmake.lua << 'EOF'
-          add_rules("mode.release")
-          set_languages("c++23")
-          package("cmdline")
-              set_homepage("https://github.com/mcpplibs/cmdline")
-              add_urls("https://github.com/mcpplibs/cmdline/archive/refs/tags/$(version).tar.gz")
-              add_versions("0.0.1", "3fb2f5495c1a144485b3cbb2e43e27059151633460f702af0f3851cbff387ef0")
-              on_install(function (package)
-                  import("package.tools.xmake").install(package)
-              end)
-          package_end()
-          add_requires("cmdline 0.0.1")
-          target("mcpp")
-              set_kind("binary")
-              add_files("src/main.cpp")
-              add_files("src/**.cppm")
-              add_packages("cmdline")
-              add_includedirs("src/libs/json")
-              set_policy("build.c++.modules", true)
-          EOF
-          xmake f -y -m release --toolchain=llvm --sdk="$LLVM_ROOT"
-          xmake build -y mcpp
-          rm -f xmake.lua
-          MCPP_BIN=$(find build -name mcpp -type f -perm +111 | head -1)
+          export PATH="$HOME/.xlings/subos/default/bin:$PATH"
+          xlings install mcpp -y
+          mcpp --version
+
+      - name: Build mcpp (self-host)
+        run: |
+          export PATH="$HOME/.xlings/subos/default/bin:$PATH"
+          mcpp build
+          MCPP_BIN=$(find target -path "*/bin/mcpp" | head -1)
           test -x "$MCPP_BIN"
           file "$MCPP_BIN"
           otool -L "$MCPP_BIN"