Issue #1621 reported an issue where bcc-lua has an unresolved
symbol bcc_resolve_symname. This is a side effect of previous
cmake file refactorization which permits better control
over what features can be enabled during build time.
The refactorization caused some symbols in bcc_syms.cc
got lost in the final link which produced bcc-lua.

This patch fixed the issue by add a new static library target
bcc-lua-static and adds bcc_syms.cc to it when the library
is created and hence preserved the symbol.

Also removed unnecessary linking for clang_frontend library.
Signed-off-by: Yonghong Song <yhs@fb.com>