Error on v1.0 with Linux cmake build

[vincentjzy]

Discussed in #10

^{Originally posted by club660 February 9, 2023}
make a OpenCorr v1.0 build with following error on 'oc_point'

error: ‘sqrt’ was not declared in this scope
42 | return sqrt(x * x + y * y);
| ^~~~

Update:
Add #include <math.h> at the beginning solve this problem.