Fix LTO (aka interprocedural optimization) build with MSVC

Also, disable MSVC LTO for static client libraries - they won't be usable
for end-users.

cmake/libutils.cmake

@@ -370,5 +370,11 @@ ENDFUNCTION()
 FUNCTION (MAYBE_DISABLE_IPO target)
   IF(MSVC AND NOT CLANG_CL)
     SET_TARGET_PROPERTIES(${target} PROPERTIES INTERPROCEDURAL_OPTIMIZATION OFF)
+    IF(CMAKE_CONFIGURATION_TYPES)
+      FOREACH(cfg ${CMAKE_CONFIGURATION_TYPES})
+        STRING(TOUPPER "${cfg}" cfg_upper)
+        SET_TARGET_PROPERTIES(${target} PROPERTIES INTERPROCEDURAL_OPTIMIZATION_${cfg_upper} OFF)
+      ENDFOREACH()
+    ENDIF()
   ENDIF()
 ENDFUNCTION()

cmake/mariadb_connector_c.cmake

@@ -40,6 +40,13 @@ SET(CLIENT_PLUGIN_PVIO_SOCKET STATIC)
 MESSAGE("== Configuring MariaDB Connector/C")
 ADD_SUBDIRECTORY(libmariadb)
 
+IF(MSVC AND TARGET mariadb_obj AND TARGET mariadbclient)
+  # With MSVC, do not produce LTCG-compiled static client libraries.
+  # They are not usable by end-users, being tied to exact compiler version
+  MAYBE_DISABLE_IPO(mariadb_obj)
+  MAYBE_DISABLE_IPO(mariadbclient)
+ENDIF()
+
 IF(UNIX)
   INSTALL(CODE "EXECUTE_PROCESS(
                   COMMAND ${CMAKE_COMMAND} -E make_directory \$ENV{DESTDIR}\${CMAKE_INSTALL_PREFIX}/${INSTALL_BINDIR})