Pre-definitions are allowed for non-embedded.
Failur catched with:
```
cmake ../../10.1 -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_COMPILER=g++-9
-DCMAKE_C_COMPILER=gcc-9 -DWITH_EMBEDDED_SERVER=ON -DCMAKE_BUILD_TYPE=Debug
-DPLUGIN_{ARCHIVE,TOKUDB,MROONGA,OQGRAPH,ROCKSDB,PERFSCHEMA,SPIDER,SPHINX}=N
-DMYSQL_MAINTAINER_MODE=ON -DNOT_FOR_DISTRIBUTION=ON
```
Alternative fix would be
```
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -201,8 +201,10 @@ LEX_STRING current_user= { C_STRING_WITH_LEN("*current_user") };
 LEX_STRING current_role= { C_STRING_WITH_LEN("*current_role") };
 LEX_STRING current_user_and_current_role= { C_STRING_WITH_LEN("*current_user_and_current_role") };

+#ifndef EMBEDDED_LIBRARY
 class ACL_USER;
 static ACL_USER *find_user_or_anon(const char *host, const char *user, const char *ip);
+#endif
```