MDEV-21362 do something with -fno-builtin-memcmp for rem0cmp.cc

innodb.cmake: restrict -fno-builtin-memcmp for GCC versions older that 4.6
where optimization issue was solved.

storage/innobase/innodb.cmake

@@ -100,7 +100,8 @@ IF(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
 #SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wconversion")
 
   IF (CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64" OR
-      CMAKE_SYSTEM_PROCESSOR MATCHES "i386")
+      CMAKE_SYSTEM_PROCESSOR MATCHES "i386" AND
+      CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.6)
     INCLUDE(CheckCXXCompilerFlag)
     CHECK_CXX_COMPILER_FLAG("-fno-builtin-memcmp" HAVE_NO_BUILTIN_MEMCMP)
     IF (HAVE_NO_BUILTIN_MEMCMP)