Manylinux1 compilation fix

Origin: PyO3/pyo3#135 (comment)

Author: gukoff

example/build-wheels.sh

@@ -9,6 +9,7 @@ export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:$HOME/rust/lib"
 
 # Compile wheels
 for PYBIN in /opt/python/cp{27,35,36}*/bin; do
+    export PYTHON_SYS_EXECUTABLE="$PYBIN/python"
     export PYTHON_LIB=$(${PYBIN}/python -c "import sysconfig; print(sysconfig.get_config_var('LIBDIR'))")
     export LIBRARY_PATH="$LIBRARY_PATH:$PYTHON_LIB"
     export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:$PYTHON_LIB"