<shlib-compat.h>: Support compat_symbol_reference for _ISOMAC

This is helpful for testing compat symbols in cases where _ISOMAC
is activated implicitly due to -DMODULE_NAME=testsuite and cannot
be disabled easily.

(cherry picked from commit 36f6e40884)

include/libc-symbols.h

@@ -59,6 +59,19 @@
 # define IN_MODULE (-1)
 #endif
 
+/* Use symbol_version_reference to specify the version a symbol
+   reference should link to.  Use symbol_version or
+   default_symbol_version for the definition of a versioned symbol.
+   The difference is that the latter is a no-op in non-shared
+   builds.  */
+#ifdef __ASSEMBLER__
+# define symbol_version_reference(real, name, version) \
+     .symver real, name##@##version
+#else  /* !__ASSEMBLER__ */
+# define symbol_version_reference(real, name, version) \
+  __asm__ (".symver " #real "," #name "@" #version)
+#endif
+
 #ifndef _ISOMAC
 
 /* This is defined for the compilation of all C library code.  features.h
@@ -396,19 +409,6 @@ for linking")
    past the last element in SET.  */
 #define symbol_set_end_p(set, ptr) ((ptr) >= (void *const *) &__stop_##set)
 
-/* Use symbol_version_reference to specify the version a symbol
-   reference should link to.  Use symbol_version or
-   default_symbol_version for the definition of a versioned symbol.
-   The difference is that the latter is a no-op in non-shared
-   builds.  */
-#ifdef __ASSEMBLER__
-# define symbol_version_reference(real, name, version) \
-     .symver real, name##@##version
-#else  /* !__ASSEMBLER__ */
-# define symbol_version_reference(real, name, version) \
-  __asm__ (".symver " #real "," #name "@" #version)
-#endif
-
 #ifdef SHARED
 # define symbol_version(real, name, version) \
   symbol_version_reference(real, name, version)