--- /dev/null
+--- a/gcc/gcc.c
++++ b/gcc/gcc.c
+@@ -9194,8 +9194,10 @@ getenv_spec_function (int argc, const ch
+ value = varname;
+
+ if (!value)
+- fatal_error (input_location,
+- "environment variable %qs not defined", varname);
++ {
++ warning (input_location, "environment variable %qs not defined", varname);
++ value = "";
++ }
+
+ /* We have to escape every character of the environment variable so
+ they are not interpreted as active spec characters. A