fix(ci): gate steamworks native libs by RUNNER_OS in Nuitka build (#1303)

#1285 added `if -f` guards but only on file presence. All platforms' libs
are checked into steamworks/, so on macOS the Linux ELF .so also passes
the check and gets fed to Nuitka, which aborts during link:

  FATAL: Error, cannot use file '.../steamworks/SteamworksPy.so'
  (ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), ...)
  to build arch 'arm64' result

Wrap the .dylib block in `$RUNNER_OS == macOS` and the .so block in
Linux. Windows is unaffected (its cmd branch only runs on Windows).

Failing run: https://github.com/Project-N-E-K-O/N.E.K.O/actions/runs/25647861208

Co-authored-by: Hongzhi Wen <cartabio.coder1@gmail.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 3 people

.github/workflows/build-desktop.yml

@@ -362,18 +362,23 @@ jobs:
           # Steam files (include if present in repo).
           # PR #1264 moved native libs into steamworks/; runtime still loads them
           # from the exe sibling dir (see steamworks/__init__.py), so dest stays at root.
+          # Gate by RUNNER_OS: all platforms' libs are checked into the repo, but
+          # feeding a Linux ELF .so to a macOS Nuitka build trips an arch-mismatch FATAL.
           NUITKA_OPTS="$NUITKA_OPTS --include-data-files=steam_appid.txt=steam_appid.txt"
-          if [ -f "steamworks/libsteam_api.dylib" ]; then
-            NUITKA_OPTS="$NUITKA_OPTS --include-data-files=steamworks/libsteam_api.dylib=libsteam_api.dylib"
-          fi
-          if [ -f "steamworks/SteamworksPy.dylib" ]; then
-            NUITKA_OPTS="$NUITKA_OPTS --include-data-files=steamworks/SteamworksPy.dylib=SteamworksPy.dylib"
-          fi
-          if [ -f "steamworks/libsteam_api.so" ]; then
-            NUITKA_OPTS="$NUITKA_OPTS --include-data-files=steamworks/libsteam_api.so=libsteam_api.so"
-          fi
-          if [ -f "steamworks/SteamworksPy.so" ]; then
-            NUITKA_OPTS="$NUITKA_OPTS --include-data-files=steamworks/SteamworksPy.so=SteamworksPy.so"
+          if [[ "$RUNNER_OS" == "macOS" ]]; then
+            if [ -f "steamworks/libsteam_api.dylib" ]; then
+              NUITKA_OPTS="$NUITKA_OPTS --include-data-files=steamworks/libsteam_api.dylib=libsteam_api.dylib"
+            fi
+            if [ -f "steamworks/SteamworksPy.dylib" ]; then
+              NUITKA_OPTS="$NUITKA_OPTS --include-data-files=steamworks/SteamworksPy.dylib=SteamworksPy.dylib"
+            fi
+          elif [[ "$RUNNER_OS" == "Linux" ]]; then
+            if [ -f "steamworks/libsteam_api.so" ]; then
+              NUITKA_OPTS="$NUITKA_OPTS --include-data-files=steamworks/libsteam_api.so=libsteam_api.so"
+            fi
+            if [ -f "steamworks/SteamworksPy.so" ]; then
+              NUITKA_OPTS="$NUITKA_OPTS --include-data-files=steamworks/SteamworksPy.so=SteamworksPy.so"
+            fi
           fi
 
           echo "=== Nuitka options ==="