x86_64-linux-deb9: Fix LLVM extraction

x86_64-linux-deb9/Dockerfile

@@ -50,7 +50,7 @@ RUN curl https://downloads.haskell.org/cabal/cabal-install-$CABAL_VERSION/cabal-
 # LLVM
 ENV LLVM_TARBALL http://releases.llvm.org/7.0.0/clang+llvm-7.0.0-x86_64-linux-gnu-ubuntu-16.04.tar.xz
 ENV PATH /opt/llvm/bin:$PATH
-RUN curl $LLVM_TARBALL | tar -xJC ..; \
+RUN curl $LLVM_TARBALL | tar -xJC .; \
     mkdir /opt/llvm; \
     cp -R clang+llvm*/* /opt/llvm; \
     rm -R clang+llvm*; \