"Undefined symbols for architecture arm64" using iOS SDK 1.4.8

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I just started integrated the iOS SDK into an app using the latest 1.4.8 iOS SDK, and have run into a problem.

When trying to get an instance to the SDK using "id <ISbtSdkApi> apiInstance = [SbtSdkFactory createSbtSdkApiInstance];", it fails to build with an arm64 architecture error:

Undefined symbols for architecture arm64:
"_deflate", referenced from:
_zipWriteInFileInZip in libsymbolbt-sdk.a(zip.o)
_zipCloseFileInZipRaw64 in libsymbolbt-sdk.a(zip.o)
"_deflateInit2_", referenced from:
_zipOpenNewFileInZip4_64 in libsymbolbt-sdk.a(zip.o)
"_inflate", referenced from:
_unzReadCurrentFile in libsymbolbt-sdk.a(unzip.o)
"_get_crc_table", referenced from:
_unzOpenCurrentFile3 in libsymbolbt-sdk.a(unzip.o)
_zipOpenNewFileInZip4_64 in libsymbolbt-sdk.a(zip.o)
"_inflateEnd", referenced from:
_unzCloseCurrentFile in libsymbolbt-sdk.a(unzip.o)
"_crc32", referenced from:
_unzReadCurrentFile in libsymbolbt-sdk.a(unzip.o)
_zipWriteInFileInZip in libsymbolbt-sdk.a(zip.o)
"_deflateEnd", referenced from:
_zipCloseFileInZipRaw64 in libsymbolbt-sdk.a(zip.o)
"_inflateInit2_", referenced from:
_unzOpenCurrentFile3 in libsymbolbt-sdk.a(unzip.o)
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Any ideas what's going wrong?