tools: add execution permission to uvwasi script

PR-URL: #47600
Reviewed-By: Yagiz Nizipli <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Michael Dawson <[email protected]>
Reviewed-By: Marco Ippolito <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>