"llvm-ar xv lib.a" from LLVM 8 doesn't print extracted object file
names. The effect of "v" is not formally specified either.
Use "llvm-ar t" to get archive member names.
Reported-by: Xueming Zhang <xuemingx.zhang@intel.com>
Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>