Getting dist-check to work:\

* Implement the FAKE_SOURCES feature for GCCLibraries/crtend \
* Search for distribution files >first< in srcdir and >second< in objdir \
* Make dist-hook only run in top level directory. \
* Make dist-check run correctly in parallel builds \
* Wrap lines to 80 cols \
* Standardize variable names

llvm-svn: 18504