Build as shared library or static library

[topazus]

In some Linux distribution, like Fedora, openSUSE or Gentoo, shared libraries are more prefered. Static libraries are suggested to be avoided to be included in packaging. It may be better to explicitly only build shared lib or static lib by using BUILD_SHARED_LIBS option. Ref: https://en.opensuse.org/openSUSE:Shared_library_packaging_policy#Best_Practices https://docs.fedoraproject.org/en-US/packaging-guidelines/#_shared_libraries https://projects.gentoo.org/qa/policy-guide/installed-files.html#pg0302 https://github.com/google/re2/issues/258

[topazus]

@ondys Could you see and review this PR?