fix llvm compilation failure

fix llvm compilation failure

Fix issue #3734

llvm upstream commit
  89eb85ac6eab [IRBuilder] Remove deprecated methods
deprecated some functions which are used by bcc.
Let us follow the above commit to use the underlying
implementation instead.

Note that I didn't create a common header for the newer
functions since b language support will be removed in
the near future.

Signed-off-by: Yonghong Song <yhs@fb.com>