WIP: Add libunwind.dll and libc++.dll into the built bin directory

This should allow running clang tests that set PATH="" before
executing binaries.

Author: mstorsjo

.github/workflows/test-windows.yml

@@ -43,6 +43,8 @@ jobs:
             -DCMAKE_CXX_COMPILER=clang++ `
             -DLLVM_LIT_ARGS="-v --time-tests"
           ninja test-depends
+          cp c:\llvm-mingw\bin\libc++.dll bin
+          cp c:\llvm-mingw\bin\libunwind.dll bin
       - name: Run tests
         run: |
           cd build