Add libarena from local rust to stage0

This was needed at least when local rust was 1.9.0 on darwin.

Fixes #35149

Author: bcully

src/etc/local_stage0.sh

@@ -58,6 +58,7 @@ case "$TARG_DIR" in
 
 cp ${PREFIX}/bin/rustc${BIN_SUF} ${TARG_DIR}/stage0/bin/
 cp ${PREFIX}/${LIB_DIR}/${RUSTLIBDIR}/${TARG_DIR}/${LIB_DIR}/* ${TARG_DIR}/stage0/${LIB_DIR}/
+cp ${PREFIX}/${LIB_DIR}/${LIB_PREFIX}arena*${LIB_SUF} ${TARG_DIR}/stage0/${LIB_DIR}/
 cp ${PREFIX}/${LIB_DIR}/${LIB_PREFIX}extra*${LIB_SUF} ${TARG_DIR}/stage0/${LIB_DIR}/
 cp ${PREFIX}/${LIB_DIR}/${LIB_PREFIX}rust*${LIB_SUF} ${TARG_DIR}/stage0/${LIB_DIR}/
 cp ${PREFIX}/${LIB_DIR}/${LIB_PREFIX}std*${LIB_SUF} ${TARG_DIR}/stage0/${LIB_DIR}/