testsuite/100176 - fix struct-layout-1_generate.c compile

With -Werror=return-type we run into compile fails complaining about
missing return stmts.

2021-04-21  Richard Biener  <rguenther@suse.de>

	PR testsuite/100176
	* g++.dg/compat/struct-layout-1_generate.c: Add missing return.
	* gcc.dg/compat/struct-layout-1_generate.c: Likewise.

(cherry picked from commit d8f953819e)

gcc/testsuite/g++.dg/compat/struct-layout-1_generate.c

@@ -983,6 +983,8 @@ subvalues (struct entry *e, char *p, char *letter)
       if (e[0].len != 0)
 	output_FNB ('B', e);
       return 1;
+    default:
+      return 0;
     }
 }
 

gcc/testsuite/gcc.dg/compat/struct-layout-1_generate.c

@@ -1280,6 +1280,8 @@ subvalues (struct entry *e, char *p, char *letter)
       if (e[0].len != 0)
 	output_FNB ('B', e);
       return 1;
+    default:
+      return 0;
     }
 }