fix: ci-fresh-install — test released mcpp, not freshly-built

Use xlings-installed mcpp directly to test:
  1. mcpp build (self-host compile)
  2. mcpp new hello → mcpp run (default toolchain)
  3. Linux: install LLVM → mcpp new → mcpp run (continue-on-error
     since released mcpp may not have latest fixes yet)

No extra env vars, no $MCPP variable — just mcpp on PATH via xlings.

Author: Sunrisepeak

.github/workflows/ci-fresh-install.yml

@@ -1,7 +1,7 @@
 name: ci-fresh-install
 
-# Fresh install CI — simulates first-time user experience on all platforms.
-# Flow: xlings install mcpp → build this PR → mcpp new hello → mcpp run
+# Fresh install CI — tests the released mcpp via xlings on clean machines.
+# Validates: xlings install mcpp → mcpp build (self) → mcpp new → mcpp run
 
 on:
   push:
@@ -22,7 +22,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Bootstrap xlings + mcpp
+      - name: Install xlings + mcpp
         env:
           XLINGS_NON_INTERACTIVE: '1'
         run: |
@@ -32,21 +32,18 @@ jobs:
           xlings install mcpp -y
           echo "$HOME/.xlings/subos/default/bin" >> "$GITHUB_PATH"
 
-      - name: Build this PR's mcpp
-        run: |
-          mcpp build
-          # Put freshly-built mcpp first on PATH so subsequent steps use it
-          MCPP_DIR=$(dirname "$(find target -type f -name mcpp -printf '%T@ %p\n' | sort -rn | head -1 | cut -d' ' -f2)")
-          echo "$MCPP_DIR" >> "$GITHUB_PATH"
+      - name: mcpp build (self-host)
+        run: mcpp build
 
-      - name: "mcpp new hello → mcpp run (GCC)"
+      - name: mcpp new hello → mcpp run
         run: |
           cd "$(mktemp -d)"
           mcpp new hello
           cd hello
           mcpp run
 
-      - name: "install LLVM → mcpp new → mcpp run"
+      - name: install LLVM → mcpp new → mcpp run
+        continue-on-error: true
         run: |
           mcpp self config --mirror GLOBAL
           mcpp toolchain install llvm 20.1.7
@@ -63,7 +60,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Bootstrap xlings + mcpp
+      - name: Install xlings + mcpp
         env:
           XLINGS_NON_INTERACTIVE: '1'
         run: |
@@ -73,13 +70,10 @@ jobs:
           xlings install mcpp -y
           echo "$HOME/.xlings/subos/default/bin" >> "$GITHUB_PATH"
 
-      - name: Build this PR's mcpp
-        run: |
-          mcpp build
-          MCPP_DIR=$(dirname "$(find target -type f -name mcpp ! -name '*.o' | head -1)")
-          echo "$(cd "$MCPP_DIR" && pwd)" >> "$GITHUB_PATH"
+      - name: mcpp build (self-host)
+        run: mcpp build
 
-      - name: "mcpp new hello → mcpp run"
+      - name: mcpp new hello → mcpp run
         run: |
           cd "$(mktemp -d)"
           mcpp new hello
@@ -93,7 +87,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Bootstrap xlings + mcpp
+      - name: Install xlings + mcpp
         shell: pwsh
         env:
           XLINGS_NON_INTERACTIVE: '1'
@@ -106,14 +100,11 @@ jobs:
           xlings install mcpp -y
           $xlingsbin | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
 
-      - name: Build this PR's mcpp
+      - name: mcpp build (self-host)
         shell: pwsh
-        run: |
-          mcpp build
-          $mcppExe = Get-ChildItem -Path target -Recurse -Filter "mcpp.exe" | Select-Object -First 1
-          $mcppExe.DirectoryName | Out-File -Append -FilePath $env:GITHUB_PATH -Encoding utf8
+        run: mcpp build
 
-      - name: "mcpp new hello → mcpp run"
+      - name: mcpp new hello → mcpp run
         shell: pwsh
         run: |
           $tmp = New-TemporaryFile | ForEach-Object { Remove-Item $_; New-Item -ItemType Directory -Path $_ }