OK, after copying
\Android\sdk\build-tools\17.0.0\aapt.exe to
\Android\sdk\platforms\android-17
compilation works again.
But, future updates of the aapt.exe won't end up there. So, a better solution is needed than manually copying the file to another directory. Maybe, a hard link in the \Android\sdk\platforms\android-17 directory will make future updates "automatic". But, hard links may be destroyed depending on how the new file is copied over the old one.