That is a standard header. If <cmath> is not available, your C++ compiler is broken. This is an Ubuntu problem, not a Perl problem, although it does cause the inability to install that Perl extension as a symptom.
Please file a bug report at Ubuntu on their broken compiler, if installing build-essential (if I remember the name correctly) does not work. Actually, file a bug report anyway — if installing build-essential (or so) fixes your problem, then libglm-dev is missing a dependency. Both of these situations are Ubuntu bugs.