[tlbuild] icu-76.2 in TL source tree, requires C++17

[Karl Berry]

    +++ ptypes.h    2024-10-29 20:16:03.319529472 +0100
    ...
    -#   if U_HAVE_CHAR16_T
    +#   if U_HAVE_CHAR16_T && U_PLATFORM_IS_LINUX_BASED

Thanks Marc.

    It works for NetBSD but I wonder if using U_PLATFORM_IS_LINUX_BASED
    is OK for other TeX Live platforms.  

No way to know without trying it. I'll put it in and we'll see what
happens.

    Should this patch be added to libs/icu/TLpatches?

Presuming it works out, yes. Or whatever is needed.

    By the way, libs/icu/TLpatches/patch-19-netbsd doesn't seem to be
    needed anymore, I suggest to remove it.

Excellent news! I will remove it. Thanks. -k