[libcxxabi][demangle] Fix the cp-to-llvm.sh sync script to copy all headers (#166572)
In https://github.com/llvm/llvm-project/pull/137947 I refactored the
script and added a `copy_files` function, which takes the header files
to copy as an argument.
But because the list of headers is a space separated string, we need to
quote the string. Otherwise we would just copy the first header in the
list.
This patch also adds an `echo` statement in the `copy_files` loop to
print the source/destination. Confirming that the files are copied as
expected.
```
$ libcxxabi/src/demangle/cp-to-llvm.sh
This will overwrite the copies of ItaniumDemangle.h ItaniumNodes.def StringViewExtras.h Utility.h in ../../../llvm/include/llvm/Demangle and DemangleTestCases.inc in ../../../llvm/include/llvm/Demangle/../Testing/Demangle; are you sure? [y/N]y
Copying ./ItaniumDemangle.h to ../../../llvm/include/llvm/Demangle/ItaniumDemangle.h
Copying ./ItaniumNodes.def to ../../../llvm/include/llvm/Demangle/ItaniumNodes.def
Copying ./StringViewExtras.h to ../../../llvm/include/llvm/Demangle/StringViewExtras.h
Copying ./Utility.h to ../../../llvm/include/llvm/Demangle/Utility.h
Copying ../../test/DemangleTestCases.inc to ../../../llvm/include/llvm/Demangle/../Testing/Demangle/DemangleTestCases.inc
```
Luckily there weren't any out-of-sync changes introduced in the
meantime.
llvm-project
d49c6707 - [libcxxabi][demangle] Fix the cp-to-llvm.sh sync script to copy all headers (#166572)
