XCode 9: Undefined symbols for architecture arm64 within RMAppReceipt

I am using RMAppReceipt to verify in app purchases within my applcation and this all worked fine in before updating to XCode 9. I have the RMAppReceipt.h , RMAppReceipt.m , RMAppStoreReceiptVerifier.h & RMAppStoreReceiptVerifier.m files added to my project as this https://github.com/robotmedia/RMStore/wiki/Receipt-verification#adding-openssl page instructs together with the 'OpenSSL-Universal' pod.

This all worked fine in XCode 8.3 but I now have the following errors after updating my code to Swift 4.0 within the ProjectNameUITests folder:

Apple Mach-O Linker (Id) Error:

Undefined symbols for architecture arm64:
"_X509_STORE_add_cert", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_ASN1_get_object", referenced from:
  +[RMAppReceipt enumerateASN1Attributes:length:usingBlock:] in RMAppReceipt.o
  _RMASN1ReadInteger in RMAppReceipt.o
  _RMASN1ReadOctectString in RMAppReceipt.o
  _RMASN1ReadString in RMAppReceipt.o
"_BIO_new", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_X509_free", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_d2i_X509", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_d2i_PKCS7_fp", referenced from:
  +[RMAppReceipt dataFromPCKS7Path:] in RMAppReceipt.o
"_PKCS7_verify", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_X509_STORE_free", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_BIO_free", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_EVP_cleanup", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_X509_STORE_new", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_OBJ_obj2nid", referenced from:
  +[RMAppReceipt dataFromPCKS7Path:] in RMAppReceipt.o
"_BIO_s_mem", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_OpenSSL_add_all_digests", referenced from:
  +[RMAppReceipt verifyPCKS7:withCertificateData:] in RMAppReceipt.o
"_PKCS7_free", referenced from:
  +[RMAppReceipt dataFromPCKS7Path:] in RMAppReceipt.o
"_SHA1", referenced from:
  -[RMAppReceipt verifyReceiptHash] in RMAppReceipt.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)