XXX: Work around missing OpenSSL from ld flags

Comes from a regression in CocoaPods 1.6+ and I don't know how to
fix it properly. Neither do I want to waste too much time on it.

README.md

@@ -68,7 +68,7 @@ Many other flags are ignored too but it's normally not an issue.
 - Xcode 10+ (Swift 4.2)
 - Git (preinstalled with Xcode Command Line Tools)
 - Ruby (preinstalled with macOS)
-- [CocoaPods 1.4.0][dep-cocoapods]
+- [CocoaPods 1.6.0][dep-cocoapods]
 - [jazzy][dep-jazzy] (optional, for documentation)
 - [Disable Bitcode][issue-51]
 

TunnelKit.podspec

@@ -16,7 +16,8 @@ Pod::Spec.new do |s|
         p.source_files          = "TunnelKit/Sources/Core/**/*.{h,m,swift}"
         p.private_header_files  = "TunnelKit/Sources/Core/**/*.h"
         p.preserve_paths        = "TunnelKit/Sources/Core/*.modulemap"
-        p.pod_target_xcconfig   = { "SWIFT_INCLUDE_PATHS" => "${PODS_TARGET_SRCROOT}/TunnelKit/Sources/Core",
+        p.pod_target_xcconfig   = { "OTHER_LDFLAGS" => "-framework openssl",
+                                    "SWIFT_INCLUDE_PATHS" => "${PODS_TARGET_SRCROOT}/TunnelKit/Sources/Core",
                                     "APPLICATION_EXTENSION_API_ONLY" => "YES" }
         p.dependency "SwiftyBeaver"
         p.dependency "OpenSSL-Apple", "~> 1.1.0i.2"