Use the new unified SOAAP_BUILD_DIR.

Since SOAAP_BUILD_DIR now incorporates the SOAAP header as well, we don't need SOAAP_SOURCE_DIR any more. This makes run-gyp ever so slightly easier to run.
Kill run-gyp if gyp_chromium or patch fail.
Use absolute path for llvm-{file-map,link-wrapper}.

These SOAAP LLVM helpers should be referred to by absolute path, so that we don't need to modify our $PATH when building SOAAP-Chromium.
Use SOAAP's new backtrace summary feature.

We often don't care about all 1,700+ entries in the stack trace, so just show the top and bottom 10 entries.
Don't output bitcode to /dev/null.

The 'soaap' binary now omits bitcode generation if it doesn't receive an '-o' flag, which speeds things up considerably. Accordingly, drop the '-o' flag and stop generating bitcode to throw away.
Provide more information on what run-gyp is doing.