Bug#1113328: nlopt: FTBFS with CMake 4

[Rebecca N. Palmer]

Control: tags -1 fixed-upstream patch

This upstream commit probably fixes this (but I haven't actually tried it):
https://github.com/stevengj/nlopt/commit/2bcac964888908ade29e42f6f8af5f0539dbe16c

Alternatively, we could update to upstream 2.10 (which includes this); 
none of the changes are *obviously* compatibility-breaking, but I 
haven't looked closely.