qtdeclarative has a header src/3rdparty/masm/stubs/wtf/unicode/utypes.h that conflicts with the icu header https://github.com/unicode-org/icu/blob/master/icu4c/source/common/unicode/utypes.h. The version bundled with qt is just a redirect for unicode/Unicode.h (which does not exist in the icu sources)

Depending on how your build is configured, this can cause problems, and since there's only one place (src/3rdparty/masm/yarr/YarrCanonicalize.h) where this include is referenced, it may make sense to modify YarrCanonicalize.h to instead just include <unicode/Unicode.h>