WindowsInstaller: more robust automatic version info from freecadcmd

otherwise it broke if freecad had other unrelated output

package/WindowsInstaller/write_version_nsh.py

@@ -0,0 +1,20 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+#
+# this script is meant to be called by nsis installer scripts, it gets version information
+# from freecad and writes version.nsh file in the directory the script is located at
+import FreeCAD
+import datetime
+import os
+
+filepath=os.path.join(os.path.dirname(os.path.abspath(__file__)),"version.nsh")
+v=FreeCAD.Version()
+content=f'''\
+!define COPYRIGHT_YEAR {datetime.date.today().year}
+!define APP_VERSION_MAJOR "{v[0]}"
+!define APP_VERSION_MINOR "{v[1]}"
+!define APP_VERSION_PATCH "{v[2]}"
+!define APP_VERSION_REVISION "{v[3].split()[0]}"
+'''
+
+with open(filepath, "w", encoding="utf-8") as file:
+    file.writelines(content)