[Fix] ci: Use Unix paths for PyInstaller spec

PyInstaller claims that either Windows or Unix paths should work, and
the old method of using Unix paths appeared to successfully generate
working Windows binaries.  I'm not sure why using Windows paths fails,
though.

For now, use Unix paths.  If necessary, "os.path.join(...)" could be
used instead.

Partially reverts b91dfdf

See https://pyinstaller.org/en/stable/spec-files.html
And https://github.com/IldarRyabkov/BubbleTanks2/blob/main/src/setup.spec

hapticpancake.spec

@@ -9,7 +9,7 @@ datas += tmp_ret[0]; binaries += tmp_ret[1]; hiddenimports += tmp_ret[2]
 
 
 a = Analysis(
-    ['BridgeApp\\main.py'],
+    ['BridgeApp/main.py'],
     pathex=[],
     binaries=binaries,
     datas=datas,
@@ -41,5 +41,5 @@ exe = EXE(
     target_arch=None,
     codesign_identity=None,
     entitlements_file=None,
-    icon=['Images\\icon.ico'],
+    icon=['Images/icon.ico'],
 )