Fix stack overflow of bash when copying tf headers

[mareikethies]

Fixes issue described in #87. Putting together the copy command for tf headers in tf_configure.bzl using " && " causes a stack overflow in msys2 bash.exe on windows. Executing each copy as a single command (via "\n") prevents this.

[akmaier]

This would also totally help my project! There might be other issues down the line and we would be glad to track and fix them!