Paths fixed.

script/ci_install.sh

 # --- LibC++
 if [[ "${CXX}" = clang* ]]
 then
-    mkdir build && cd build
-
     if [[ ! -d "$(ls -A ${DEPENDENCY_DIR}/llvm-source)" ]]
     then
         LLVM_RELEASE=release_50
         git clone --depth=1 -b ${LLVM_RELEASE} https://github.com/llvm-mirror/libcxx.git llvm-source/projects/libcxx
         git clone --depth=1 -b ${LLVM_RELEASE} https://github.com/llvm-mirror/libcxxabi.git llvm-source/projects/libcxxabi
 
+        mkdir build && cd build
 
         cmake -DCMAKE_C_COMPILER=${CC} \
                 -DCMAKE_CXX_COMPILER=${CXX} \
                 -DCMAKE_INSTALL_PREFIX=/usr \
                 ../llvm-source
         make cxx -j4
+    else
+        cd build
     fi
 
     sudo make install-cxxabi install-cxx