Update CMakeLists.txt

Merge pull request fastfloat#49 from fastfloat/dlemire/cleaner19

Trying alternate handling of overflows.

Merge pull request fastfloat#48 from fastfloat/dlemire/fix_issue_47

Fixes issue 47

Merge pull request fastfloat#46 from fastfloat/dlemire/more_tests

Adding more CI tests and adds support for clang under msys2

Merge pull request fastfloat#41 from biojppm/fix/bloated_binary

remove 1.1MB (85%) of binary size by not including iostream

Merge pull request fastfloat#38 from lemire/dlemire/issue37

Adding support for big endian systems

Actually, 19.