While working on gdb-add-index.sh, it appeared that it uses the non
POSIX 'local' keyword. Instead of using local to allow variable
shadowing, I rename the local one to avoid name conflicts altogether.
This commit gets rid of the following shellcheck warning:
In gdb-add-index.sh line 63:
local file="$1"
^--------^ SC2039: In POSIX sh, 'local' is undefined.
gdb/ChangeLog:
* contrib/gdb-add-index.sh: Avoid variable shadowing and get
rid of 'local'.