st/clover: Fix build against LLVM 3.8 SVN r244928

st/clover: Fix build against LLVM 3.8 SVN r244928

raw_svector_ostream::flush() is now unnecessary and forbidden:

  CXX      llvm/libclllvm_la-invocation.lo
../../../../../src/gallium/state_trackers/clover/llvm/invocation.cpp: In function 'clover::module {anonymous}::build_module_llvm(llvm::Module*, unsigned int (&)[7])':
../../../../../src/gallium/state_trackers/clover/llvm/invocation.cpp:574:29: error: use of deleted function 'void llvm::raw_svector_ostream::flush()'
       bitcode_ostream.flush();
                             ^
In file included from /home/daenzer/src/llvm-git/llvm/include/clang/Basic/VirtualFileSystem.h:22:0,
                 from /home/daenzer/src/llvm-git/llvm/include/clang/Basic/FileManager.h:20,
                 from /home/daenzer/src/llvm-git/llvm/include/clang/Basic/SourceManager.h:38,
                 from /home/daenzer/src/llvm-git/llvm/include/clang/Frontend/CompilerInstance.h:16,
                 from ../../../../../src/gallium/state_trackers/clover/llvm/invocation.cpp:25:
/home/daenzer/src/llvm-git/llvm/include/llvm/Support/raw_ostream.h:512:8: note: declared here
   void flush() = delete;
        ^
Makefile:862: recipe for target 'llvm/libclllvm_la-invocation.lo' failed

Reviewed-by: Francisco Jerez <currojerez@riseup.net>