Use 1.0 version of grpc-swift

[e-sung]

Summary

Hi! Thank you for your amazing open-source work!
Recently 1.0 version of grpc-swift was released.
I think many people would like to use officially released version of grpc-swift!

Changes

• Update GRPC_SWIFT_VERSION in build.sh
• Because grpc-swift 1.0 depends on swift5.2, also updated SWIFT_VERSION

[rvolosatovs]

Thank you for contribution!

Could you fix

install: cannot stat '/grpc-swift/protoc-gen-swift': No such file or directory
The command '/bin/sh -c mkdir -p /grpc-swift &&     curl -sSL https://api.github.com/repos/grpc/grpc-swift/tarball/${GRPC_SWIFT_VERSION} | tar xz --strip 1 -C /grpc-swift &&     cd /grpc-swift && make &&     install -Ds /grpc-swift/protoc-gen-swift /protoc-gen-swift/protoc-gen-swift &&     install -Ds /grpc-swift/protoc-gen-grpc-swift /protoc-gen-swift/protoc-gen-grpc-swift &&     cp /lib64/ld-linux-x86-64.so.2         $(ldd /protoc-gen-swift/protoc-gen-swift /protoc-gen-swift/protoc-gen-grpc-swift | awk '{print $3}' | grep /lib | sort | uniq)         /protoc-gen-swift/ &&     find /protoc-gen-swift/ -name 'lib*.so*' -exec patchelf --set-rpath /protoc-gen-swift {} \; &&     for p in protoc-gen-swift protoc-gen-grpc-swift; do         patchelf --set-interpreter /protoc-gen-swift/ld-linux-x86-64.so.2 /protoc-gen-swift/${p};     done' returned a non-zero code: 1

in the build?

Also, does this close #57 as well?

[e-sung]

It seems like tarball from https://api.github.com/repos/grpc/grpc-swift/tarball/ doesn't contain all the necessary ingredients. I'll look further on this weekend!

[rvolosatovs]

LGTM, thanks!