[tlbuild] [tlbuilders] llvm-11 compiler bug fix

[Mojca Miklavec]

On Sat, 27 Feb 2021 at 20:33, Nelson H. F. Beebe wrote:
>
> The LLVM team announced today a bug fix for a broken ABI in the 11.0.1
> compilers.  Because some systems now use that compiler family for
> /usr/bin/cc, the bug might affect some TeX Live 2021 builds.

I just wanted to add that clang 11 is no longer able to compile icu on
older macOS versions after these two changes:
    https://reviews.llvm.org/D83250
    https://unicode-org.atlassian.net/browse/ICU-13440

Mojca