[llvm] [Offload] Fix missing dependencies in Offload API generation (PR #142776)

[Krzysztof Parzyszek via llvm-commits]

kparzysz wrote:

The generation fails if the "generated" and "include" subdirectories are missing.

runtimes/runtimes-bins/offload/plugins-nextgen/common/include
runtimes/runtimes-bins/offload/liboffload/API/generated

https://github.com/llvm/llvm-project/pull/142776