force linking the whole api-static library into shared library

When a static library is linked to produce a shared library,
only referenced symbols in the static library eventually
gets linked.

api-static library has entry points for C++ API.
Many symbols in this library do not have references
outside of this library and will get dropped during
linking process.

This patch forces the linking of the whole api-static
library in order to procude bcc shared library.

Reported-by: Mauricio Vasquez <mauricio.vasquez@polito.it>
Signed-off-by: Yonghong Song <yhs@fb.com>