* Add toolchain to Docker image

This is not the problem for plain DROP DATABASE query since it first
remove tables.

  (gdb) bt
  0  __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:103
  1  0x00007f353c262774 in __GI___pthread_mutex_lock (mutex=mutex@entry=0x11049288 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog+8>) at ../nptl/pthread_mutex_lock.c:80
  2  0x0000000004fd5d1e in DB::pthread_mutex_lock (arg=arg@entry=0x11049288 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog+8>) at ../src/Common/ThreadFuzzer.cpp:253
  3  0x000000000c70b3a9 in std::__1::__libcpp_mutex_lock (__m=__m@entry=0x11049288 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog+8>) at ../contrib/libcxx/include/__threading_support:322
  4  std::__1::mutex::lock (this=this@entry=0x11049288 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog+8>) at ../contrib/libcxx/src/mutex.cpp:33
  5  0x0000000008acd4e2 in std::__1::lock_guard<std::__1::mutex>::lock_guard (__m=..., this=<synthetic pointer>) at ../contrib/libcxx/include/__mutex_base:90
  6  DB::DatabaseCatalog::removeDependency (this=this@entry=0x11049280 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog>, from=..., where=...) at ../src/Interpreters/DatabaseCatalog.cpp:388
  7  0x000000000975044b in DB::StorageMaterializedView::shutdown (this=0x7f338d178a00) at ../src/Storages/StorageMaterializedView.cpp:362
  8  0x0000000008a79602 in DB::DatabaseWithOwnTablesBase::shutdown (this=0x7f353be3cc60) at ../contrib/libcxx/include/__tree:184
  9  0x0000000009546196 in DB::DatabaseWithDictionaries::shutdown (this=0x7f353be3cc60) at ../src/Databases/DatabaseWithDictionaries.cpp:265
  10 0x0000000008acecdb in DB::DatabaseCatalog::detachDatabase (this=0x11049280 <DB::DatabaseCatalog::init(DB::Context const*)::database_catalog>, database_name=..., drop=drop@entry=false, check_empty=check_empty@entry=false) at ../contrib/libcxx/include/memory:3826
  11 0x0000000004bf0aa5 in DB::InterpreterCreateQuery::createDatabase (this=0x7ffd6e1bab80, create=...) at ../src/Interpreters/InterpreterCreateQuery.cpp:162
  12 0x0000000008b04327 in DB::InterpreterCreateQuery::execute (this=this@entry=0x7ffd6e1bab80) at ../src/Interpreters/InterpreterCreateQuery.cpp:722
  13 0x0000000008d0fdaa in DB::executeCreateQuery (has_force_restore_data_flag=false, file_name=..., database=..., context=..., query=...) at ../src/Interpreters/loadMetadata.cpp:48
  14 DB::loadDatabase (context=..., database=..., database_path=..., force_restore_data=<optimized out>) at ../src/Interpreters/loadMetadata.cpp:72
  15 0x0000000008d103c3 in DB::loadMetadata (context=...) at ../src/Interpreters/loadMetadata.cpp:111
  16 0x0000000004f4d25e in DB::Server::main (this=<optimized out>) at ../contrib/libcxx/include/memory:2582
  17 0x000000000bbc8963 in Poco::Util::Application::run (this=this@entry=0x7ffd6e1bcc60) at ../contrib/poco/Util/src/Application.cpp:334
  18 0x0000000004ffe1de in DB::Server::run (this=0x7ffd6e1bcc60) at ../programs/server/Server.cpp:178
  19 0x0000000004ff36cc in mainEntryClickHouseServer (argc=3, argv=0x7f353be58bc0) at ../programs/server/Server.cpp:1060
  20 0x0000000004f49b99 in main (argc_=<optimized out>, argv_=<optimized out>) at ../contrib/libcxx/include/vector:655