subdirectories to traverse into.
 - Originally I wanted to avoid this and just autoscan, but this has one key
   flaw in that new subdirectories can not automatically trigger a rerun of the
   llvm-build tool. This is particularly a pain when switching back and forth
   between trees where one has added a subdirectory, as the dependencies will
   tend to be wrong. This will also eliminates FIXME implicitly.

llvm-svn: 146436

llvm-svn: 146409

LLVMBuild: Add explicit information on whether targets define an assembly printer, assembly parser, or disassembler.

llvm-svn: 144344

handle defining the "magic" target related components (like native,
nativecodegen, and engine).
 - We still require these components to be in the project (currently in
   lib/Target) so that we have a place to document them and hopefully make it
   more obvious that they are "magic".

llvm-svn: 144253

 - Gives us a place to hang target specific metadata (like whether the target has a JIT).

llvm-svn: 144250

llvm-svn: 143634