macOS builds broken for release branches

[Mark Rotteveel]

It seems the macOS builds are broken for the release branches. They fail
with errors:

v5.0-release: "configure: error: ICU support not found - please install
development ICU package"

v4.0-release and B3_0_Release: "ld: Shared cache eligible dylibs cannot
use '-undefined dynamic_lookup' or '-U' to find symbols. Remove these
options or opt out of the shared cache using the build setting
'LD_SHARED_CACHE_ELIGIBLE=NO' (or linker flag '-not_for_dyld_shared_cache')
clang: error: linker command failed with exit code 1 (use -v to see
invocation)"

(I've listed the last error, there may be earlier errors)

Can someone look at this?

Mark
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Mark Rotteveel