Missing -lm breaks build on armv7hl

[pterjan]

Describe the bug
Build failure on armv7hl

/usr/bin/ld: build/temp.linux-armv8l-3.10/src/numbers.o: in function `_PyFloat_is_Intlike':
/home/iurt/rpmbuild/BUILD/fastnumbers-3.2.1/src/numbers.c:69: undefined reference to `floor'

As the code uses floor() it should set -lm when linking. I guess on other architectures something else is already pulling in -lm so it was not noticed.

Adding extra_link_args=["-lm"]to setup.py fixes it.

Environment (please complete the following information):

• fastnumbers version: 3.2.1
• Python Version: 3.10
• OS: Mageia
• Compiler (if known): gcc 11.2