Clang Scan-Build Plugin needs updating to handle newer scan-build output directory layout

The scan-build plugin expects detail reports to be in the same directory as the index.html file.

Starting with checker-271 the output directory layout seems to have changed. The index.html file is still in the top-level output directory, but the individual detail reports are in a subdirectory that looks like this:

% tree -d

.
└── Project.build
    └── Debug
        └── Target.build
            └── StaticAnalyzer
                └── normal
                    └── i386