build win/mac: do not pass custom args to pyinstaller; use envvars

custom args no longer work with pyinstaller 5.0 (see https://github.com/pyinstaller/pyinstaller/issues/6762 )

```
option(s) not allowed:
  ...
makespec options not valid when a .spec file is given
```

contrib/osx/osx.spec

@@ -10,11 +10,8 @@ MAIN_SCRIPT='run_electrum'
 ICONS_FILE=PYPKG + '/gui/icons/electrum.icns'
 
 
-for i, x in enumerate(sys.argv):
-    if x == '--name':
-        VERSION = sys.argv[i+1]
-        break
-else:
+VERSION = os.environ.get("ELECTRUM_VERSION")
+if not VERSION:
     raise Exception('no version')
 
 electrum = os.path.abspath(".") + "/"