build: Remove other unneeded linkages to standard libraries.

-ldl Dynamic Linker library
    Although the header is included in osal_dynamiclib_unix.c, we are
    apparently not using any of its features in our build.

-llog Android Logging library
    Not needed by audio-sdl or rsp-hle.

-lz ZLib Compression library
    Not needed by png because png is static. Rather, the clients of png
    must link to ZLib (gles2rice).