Fix a bug in handling of `PACKAGE_MAKE_INSTALL_TARGET`

plugins/python-build/bin/python-build

@@ -752,6 +752,7 @@ build_package_standard_install() {
 
   local PACKAGE_MAKE_INSTALL_OPTS="${package_var_name}_MAKE_INSTALL_OPTS"
   local PACKAGE_MAKE_INSTALL_OPTS_ARRAY="${package_var_name}_MAKE_INSTALL_OPTS_ARRAY[@]"
+  local PACKAGE_MAKE_INSTALL_TARGET="${package_var_name}_MAKE_INSTALL_TARGET"
 
   { "$MAKE" "${!PACKAGE_MAKE_INSTALL_TARGET:-install}" $MAKE_INSTALL_OPTS ${!PACKAGE_MAKE_INSTALL_OPTS} "${!PACKAGE_MAKE_INSTALL_OPTS_ARRAY}"
   } >&4 2>&1