don't override libc code in a glibc-specific way when not using glibc

sandbox/linux/services/libc_urandom_override.cc

Index: sandbox/linux/services/libc_urandom_override.cc
diff --git a/sandbox/linux/services/libc_urandom_override.cc b/sandbox/linux/services/libc_urandom_override.cc
index dfb4c269e3ffd10a14f425ceae1580474767372d..8af42ebbcf1f26e13a2e6a26bee2501da4ef00e7 100644
--- a/sandbox/linux/services/libc_urandom_override.cc
+++ b/sandbox/linux/services/libc_urandom_override.cc
@@ -59,6 +59,7 @@ static void InitLibcFileIOFunctions() {
     g_libc_fopen64 = g_libc_fopen;
   }
 
+#if defined(LIBC_GLIBC)
   // TODO(sergeyu): This works only on systems with glibc. Fix it to
   // work properly on other systems if necessary.
   g_libc_xstat = reinterpret_cast<XstatFunction>(
@@ -155,7 +156,8 @@ int xstat64_override(int version, const char *path, struct stat64 *buf) {
     return g_libc_xstat64(version, path, buf);
   }
 }
+#endif  // defined(LIBC_GLIBC)
 
-#endif  // !ADDRESS_SANITIZER
+#endif  // !defined(ADDRESS_SANITIZER)
 
 }  // namespace content