ld.so.8: Document the --argv0 option added in glibc 2.33

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man8/ld.so.8

@@ -193,6 +193,13 @@ set from a shell,
 to prevent their expansion as shell or environment variables.
 .SH OPTIONS
 .TP
+.BR \-\-argv0 " \fIstring\fP (since glibc 2.33)"
+Set
+.I argv[0]
+to the value
+.I string
+before running the program.
+.TP
 .BI \-\-audit " list"
 Use objects named in
 .I list