Fix the missing socket options for 32-bit. (#1918)

Motivation:

When pulling out the NIOBSDSocket later in #1907 we dropped some of the
socket option fixes for 32 bit platforms, which broke them.

Modifications:

Restore the socket options.

Result:

32-bit build should be working again.

Author: Lukasa

Package.swift

@@ -17,7 +17,7 @@ import PackageDescription
 
 var targets: [PackageDescription.Target] = [
     .target(name: "NIOCore",
-            dependencies: ["NIOConcurrencyHelpers"]),
+            dependencies: ["NIOConcurrencyHelpers", "CNIOLinux"]),
     .target(name: "NIO",
             dependencies: ["CNIOLinux",
                            "CNIODarwin",

Sources/NIO/System.swift

@@ -48,8 +48,6 @@ extension ipv6_mreq { // http://lkml.iu.edu/hypermail/linux/kernel/0106.1/0080.h
     }
 }
 #if arch(arm)
-let SO_RCVTIMEO = SO_RCVTIMEO_OLD
-let SO_TIMESTAMP = SO_TIMESTAMP_OLD
 let S_IFSOCK = UInt32(SwiftGlibc.S_IFSOCK)
 let S_IFMT = UInt32(SwiftGlibc.S_IFMT)
 let S_IFREG = UInt32(SwiftGlibc.S_IFREG)
@@ -59,12 +57,6 @@ let S_IFBLK = UInt32(SwiftGlibc.S_IFBLK)
 #endif
 #endif
 
-// Work around SO_TIMESTAMP/SO_RCVTIMEO being awkwardly defined in glibc.
-#if os(Linux)
-let SO_TIMESTAMP = CNIOLinux_SO_TIMESTAMP
-let SO_RCVTIMEO = CNIOLinux_SO_RCVTIMEO
-#endif
-
 // Declare aliases to share more code and not need to repeat #if #else blocks
 #if !os(Windows)
 private let sysClose = close

Sources/NIOCore/BSDSocketAPI.swift

@@ -56,6 +56,7 @@ import func WinSDK.inet_ntop
 import func WinSDK.inet_pton
 #elseif os(Linux) || os(Android)
 import Glibc
+import CNIOLinux
 
 private let sysInet_ntop: @convention(c) (CInt, UnsafeRawPointer?, UnsafeMutablePointer<CChar>?, socklen_t) -> UnsafePointer<CChar>? = inet_ntop
 private let sysInet_pton: @convention(c) (CInt, UnsafePointer<CChar>?, UnsafeMutableRawPointer?) -> CInt = inet_pton
@@ -66,6 +67,15 @@ private let sysInet_ntop: @convention(c) (CInt, UnsafeRawPointer?, UnsafeMutable
 private let sysInet_pton: @convention(c) (CInt, UnsafePointer<CChar>?, UnsafeMutableRawPointer?) -> CInt = inet_pton
 #endif
 
+// Work around SO_TIMESTAMP/SO_RCVTIMEO being awkwardly defined in glibc.
+#if os(Android) && arch(arm)
+let SO_RCVTIMEO = SO_RCVTIMEO_OLD
+let SO_TIMESTAMP = SO_TIMESTAMP_OLD
+#elseif os(Linux)
+let SO_TIMESTAMP = CNIOLinux_SO_TIMESTAMP
+let SO_RCVTIMEO = CNIOLinux_SO_RCVTIMEO
+#endif
+
 public enum NIOBSDSocket {
 #if os(Windows)
     public typealias Handle = SOCKET