Some paths are not captured properly (not absoulte path)

[HansolChoe]

In some cases, paths in projects.json are not recorded in absolute path.

If you capture the build information of gzip-1.11, you may see logs like below:

$ ./configure && cxbuild capture make -j10
...
> eXtension of Compilation Database
-- [Analyzing build Activities]
-- [Build trace preprocessed]
-- [project.json written [/home/vagrant/workspace/gzip-1.11/.xdb/project.json]]
-- [compile_commands.json written [/home/vagrant/workspace/gzip-1.11/.xdb/compile_commands.json]]
  > All dependency should start with '//'. Ignore 'threadlib.c'.
  > All dependency should start with '//'. Ignore 'lock.c'.
-- [artifacts.zip written [/home/vagrant/workspace/gzip-1.11/.xdb/artifacts.zip]]

threadlib.c and lock.c are not absolute path.
In this case, cxbuild is not killed, but it prints warning messages and ignores the two files.

These files may be okay to ignore, but we need to know when these things happen.

[HansolChoe]

I've found that threadlib.c and lock.c is realated to -dumpbase option.
-dumpbase is one of the cc1 options.