Add icu-uc to pkg-config library
On macOS with icu4c 76, we see:
Undefined symbols for architecture arm64:
"_ucnv_close_76", referenced from:
_convertToUtf16 in 000003.o
_convertFromUtf16 in 000003.o
"_ucnv_fromUChars_76", referenced from:
_convertFromUtf16 in 000003.o
"_ucnv_open_76", referenced from:
_convertToUtf16 in 000003.o
_convertFromUtf16 in 000003.o
"_ucnv_toUChars_76", referenced from:
_convertToUtf16 in 000003.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
This symbols appear to be in the icu-uc library now.