test-generated-code2: Ignore -Wdeclaration-after-statement

This file uses declarations after statements and fixing it would make
the code less readable, so silence this particular diagnostic in this
particular file.

t/generated-code2/test-generated-code2.c

@@ -5,6 +5,9 @@
 #include "t/test-optimized.pb-c.h"
 #include "t/generated-code2/test-full-cxx-output.inc"
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeclaration-after-statement"
+
 #define TEST_ENUM_SMALL_TYPE_NAME   Foo__TestEnumSmall
 #define TEST_ENUM_SMALL(shortname)   FOO__TEST_ENUM_SMALL__##shortname
 #define TEST_ENUM_TYPE_NAME   Foo__TestEnum