[libunwind] [runtimes] Fix parsing of LIB{CXX,CXXABI,UNWIND}_TEST_PARAMS (PR #67691)

[Alexander Richardson via cfe-commits]

arichardson wrote:

> @arichardson , works fine on the builders locally. Thank you. Would yo merge these changes if they are ready?

Thanks for testing! I'll merge these changes as soon as @ldionne is happy with the new macros. Once that happens I'll push the first commit manually and then merge the second one via the github UI (since we can't do "rebase and merge" due to repo settings).

https://github.com/llvm/llvm-project/pull/67691