[analyzer] Prevent ccc/c++-analyzer from hanging on Windows.

'fork'+'exec' combination made scan-build and ccc-analyzer hang under Windows. The patch replaces 'fork'+'exec' with more reliable 'system' (ccc-analyzer) and piped 'open' (scan-build). See http://reviews.llvm.org/D8774 and http://reviews.llvm.org/D9357 for more details.

llvm-svn: 241201