fix shell errors

configure_build.sh

@@ -25,6 +25,7 @@ if [ -n "$IS_MACOS" ]; then
         ARCH_FLAGS=${ARCH_FLAGS:-"-arch arm64"}
     elif [[ $PLAT == universal2 ]]; then
         # Do nothing as we are going with fusing wheels
+        ARCH_FLAGS=${ARCH_FLAGS:-}
     else
         echo "invalid platform = '$PLAT', supported values are 'intel' or 'x86_64' or 'arm64' or 'universal2'"
         exit 1

osx_utils.sh

@@ -103,7 +103,7 @@ function macpython_sdk_list_for_version {
     local _major=${_ver%%.*}
     local _return
 
-    if [ "${PLAT:-}" == "arm64" ] || [ "${PLAT:-}" == "universal2" ]; then
+    if [ "${PLAT}" = "arm64" ] || [ "${PLAT}" = "universal2" ]; then
         _return="11.0"
     elif [ "$_major" -eq "2" ]; then
         [ $(lex_ver $_ver) -lt $(lex_ver 2.7.18) ] && _return="10.6"