File _patchinfo of Package patchinfo

<patchinfo incident="3375">
  <category>recommended</category>
  <rating>moderate</rating>
  <packager>namtrac</packager>
  <summary>recommended udpate for llvm</summary>
  <description>This recommended udpate for llvm fixes the following issue:
- Conditionalize libcxx{abi} build on build_libcxx variable
- Turn libc++.so into an ldscript so it links to libc++abi automatically.</description>
</patchinfo>