Use builtin intrinsics on intel

[white238]

I ran into a bit of a mystery when I updated to fmt 8.0.1.

I got the following build error on intel 18.0.2:

fmt/format-inl.h(1923): error: identifier "ctz" is undefined
    int t = ctz(n);
            ^

In file included from fmt/format.h(2825),
                 from fmt/fmt.hpp(14),

The mystery is that fmt 8.0.1 did compiled on intel 19.0.4 but I am just not sure why intel 19 worked without this fix.

I tested this fix on intel 18, 19, and 2021.

Here is a godbolt example that shows intel has __builtin_ctz but not __has_builtin:

https://godbolt.org/z/xKrcaas8n

Intel Compiler Differences
intel 18 seems to be broken on godbolt but I tested it on our cluster
intel 2021 does have __has_builtin

[vitaut]

LGTM but could you move the ICC check after FMT_HAS_BUILTIN? Same below.

#if (FMT_GCC_VERSION || FMT_HAS_BUILTIN(__builtin_clz) || FMT_ICC_VERSION) && !FMT_MSC_VER

[white238]

done.

[vitaut]

Thank you