Make ffmpeg static again and fix Linux build in general.
Make ffmpeg static again and fix Linux build in general.

* Use $TARGET_DIR, not /usr/local, as prefix in Linux builds
  of OpenSSL and zlib. This problem was not affecting Docker
  builds because you have root rights there, but building
  outside Docker was no longer possible.

* ffmpeg --extra-ldexeflags '-static' is vital in getting an actually
  static build. '-Bstatic' is for something else and was useless
  in this context.

* librtmp now needs to include openssl/ssl.h from
  $TARGET_DIR/include path. "INC=" entry is added to
  the Makefile.

* Disable x265 CLI target because it is not needed.

* x265.pc: -lgcc_s must be replaced with -lgcc_eh.
  Unfortunately, due to how x265 CMakeLists.txt is constructed,
  this cannot be done in any other way than just replacing it
  with 'sed' after the file has been already created.

zimbatm/ffmpeg-static,zimbatm/ffmpeg-static