fix: save mcpp binary before clean in toolchain smoke tests

mcpp clean deletes target/ which contains the freshly-built binary.
Copy it to /tmp before running clean so it survives.

Also: clear Windows BMI cache (--bmi-cache) to avoid MSVC version
mismatch errors from stale std.pcm.

Author: Sunrisepeak

.github/workflows/ci-macos.yml

@@ -311,6 +311,8 @@ jobs:
           MCPP=$(find target -path "*/bin/mcpp" | head -1)
           MCPP=$(cd "$(dirname "$MCPP")" && pwd)/$(basename "$MCPP")
           test -x "$MCPP"
+          cp "$MCPP" /tmp/mcpp-fresh
+          MCPP=/tmp/mcpp-fresh
           "$MCPP" toolchain default llvm@20.1.7
           "$MCPP" clean
           "$MCPP" build

.github/workflows/ci-windows.yml

@@ -104,10 +104,12 @@ jobs:
         shell: bash
         run: |
           export MCPP_VENDORED_XLINGS="$XLINGS_BIN"
-          "$MCPP_SELF" toolchain default llvm@20.1.7
-          "$MCPP_SELF" clean
-          "$MCPP_SELF" build
-          "$MCPP_SELF" --version
+          cp "$MCPP_SELF" /tmp/mcpp-fresh.exe
+          MCPP=/tmp/mcpp-fresh.exe
+          "$MCPP" toolchain default llvm@20.1.7
+          "$MCPP" clean --bmi-cache
+          "$MCPP" build
+          "$MCPP" --version
 
       - name: Package Windows release zip
         id: package

.github/workflows/ci.yml

@@ -128,25 +128,28 @@ jobs:
           "$MCPP" toolchain default gcc@16.1.0
           bash tests/e2e/run_all.sh
 
-      - name: "Toolchain: GCC — build mcpp + test"
+      - name: Save freshly-built mcpp for toolchain tests
         run: |
           MCPP=$(realpath "$(find target -type f -name mcpp -printf '%T@ %p\n' | sort -rn | head -1 | cut -d' ' -f2)")
+          cp "$MCPP" /tmp/mcpp-fresh
+          echo "MCPP=/tmp/mcpp-fresh" >> "$GITHUB_ENV"
+
+      - name: "Toolchain: GCC — build mcpp + test"
+        run: |
           "$MCPP" toolchain default gcc@16.1.0
           "$MCPP" clean
           "$MCPP" build
           "$MCPP" test
 
       - name: "Toolchain: musl-gcc — build mcpp"
         run: |
-          MCPP=$(realpath "$(find target -type f -name mcpp -printf '%T@ %p\n' | sort -rn | head -1 | cut -d' ' -f2)")
           "$MCPP" toolchain install gcc 15.1.0-musl
           "$MCPP" toolchain default gcc@15.1.0-musl
           "$MCPP" clean
           "$MCPP" build
 
       - name: "Toolchain: LLVM — build mcpp"
         run: |
-          MCPP=$(realpath "$(find target -type f -name mcpp -printf '%T@ %p\n' | sort -rn | head -1 | cut -d' ' -f2)")
           "$MCPP" toolchain install llvm 20.1.7
           "$MCPP" toolchain default llvm@20.1.7
           "$MCPP" clean