allow using the pod together with 'use_frameworks!'

[adrian-gierakowski]

having OpenSSL as dependency causes the following problem ( can't use it together with if we specify 'use_frameworks!' in the podfile ):
CocoaPods/CocoaPods#3583

since in order to user pods written in Swift it is necessary to add 'use_frameworks!' in the podfile, it makes it impossible to SCPStoreKitManager and Swift pods in the same project

it seems like using BoringSSL could solve the problem:
https://cocoapods.org/pods/BoringSSL
grpc/grpc#4235

thanks!

[adrian-gierakowski]

seems like BoringSSL is missing some functionality required by SCPStoreKitManager ( PKCS7 )

for now our workaround is to include source of SCPStoreKitManager directly into our tree ( instead of adding the pod ) and then add OpenSSL pod on the pdofile. OpenSSL imports in SCPStoreKitManager have to be changed to use framework paths ( eg. : #import "x509.h -> #import <OpenSSL/x509.h> )