mysql57 cmake: support building

Some tests are still failed.

CMakeLists.txt

@@ -186,6 +186,12 @@ else()
 endif()
 find_path(MYSQL_CONFIG "${MYSQL_CONFIG}")
 
+if(EXISTS "${MYSQL_SOURCE_DIR}/storage/maria")
+  set(MYSQL_VARIANT "MariaDB")
+else()
+  set(MYSQL_VARIANT "MySQL")
+endif()
+
 if(EXISTS "${MYSQL_SOURCE_DIR}/pcre")
   set(MYSQL_REGEX_INCLUDE_DIR "${MYSQL_SOURCE_DIR}/pcre")
 else()
@@ -354,8 +360,11 @@ else()
     mrn_build_flag("-Wno-strict-aliasing")
     mrn_build_flag("-Wno-deprecated")
     mrn_check_cxxflag("-fno-implicit-templates")
-    mrn_check_cxxflag("-fno-exceptions")
-    mrn_check_cxxflag("-fno-rtti")
+    if("${MYSQL_VARIANT}" STREQUAL "MySQL" AND
+        ${MYSQL_VERSION} VERSION_LESS "5.7.0")
+      mrn_check_cxxflag("-fno-exceptions")
+      mrn_check_cxxflag("-fno-rtti")
+    endif()
     mrn_check_cxxflag("-felide-constructors")
   endif()
   set_source_files_properties(${MRN_SOURCES} PROPERTIES