In commit 94d0bb4d (MDEV-20377)
we replaced some inline assembler code with calls to GCC-style
builtin functions. These functions would only be available if
the target allows SSE4.2 instructions to be used. Hence, the
cmake -DWITH_MSAN=ON build would fail unless the default x86 (IA-32)
or AMD64 target was overridden.

It turns out that the problem can be solved by overriding the default
target architecture for specific functions with the help of GCC function
attributes.

ut_crc32c_8(), ut_crc32c_64(): Use the compiler-builtin intrinsic
functions. For GCC before 5, the header file <nmmintrin.h> does not
really work, and we must keep using the compiler built-in functions.

For the Microsoft compiler, we will keep using <intrin.h> because
we will also need the definition of the __cpuid() function.
On GCC and clang, we prefer to invoke inline assembler for that.

Curiously, the inline assembler in has_sse4_2() or crc32_pclmul()
is not causing any trouble for MSAN. Also, the inline assembler
in WolfSSL appears to be fine now. Something might have changed
between clang-8 and clang-10 (10.0.1).