[builtins][test] XFAIL two SPARC tests

Two SPARC builtins tests are currently FAILing due to codegen bugs:

  Builtins-sparc-sunos :: divtc3_test.c
  Builtins-sparcv9-sunos :: compiler_rt_logbl_test.c
  Builtins-sparcv9-sunos :: divtc3_test.c

I'd like to XFAIL them to reduce testsuite noise. 
  
Done as follows, tested on sparcv9-sun-solaris2.11 and x86_64-pc-solaris2.11.

Differential Revision: https://reviews.llvm.org/D64796

llvm-svn: 367295