fix(build): fix shell syntax error in smoke_test_imports heredoc

The 'cmd <<EOF || { ... }' pattern confuses bash's parser — the closing
brace of the inline error block collides with the function's closing
brace. Rewrote to capture the python script into a local var via
$(cat <<EOF), then run it with -c and a plain 'if !' guard.

build-common.sh

@@ -217,10 +217,8 @@ smoke_test_imports() {
     # installation — Pillow for example is only a Windows dep. But if a
     # module's top-level package dir exists in site-packages and we
     # can't import it, that's a broken install and we abort.
-    PYTHONPATH="$pypath" "$py_cmd" - "$sp_dir" <<'PYEOF' || {
-        echo "  ERROR: smoke test failed — site-packages is broken, aborting build"
-        return 1
-    }
+    local smoke_script
+    smoke_script=$(cat <<'PYEOF'
 import importlib
 import os
 import sys
@@ -266,4 +264,10 @@ if failed:
 
 print(f'  Smoke test passed ({tested} imported, {skipped} not installed)')
 PYEOF
+)
+
+    if ! PYTHONPATH="$pypath" "$py_cmd" -c "$smoke_script" "$sp_dir"; then
+        echo "  ERROR: smoke test failed — site-packages is broken, aborting build"
+        return 1
+    fi
 }