Functions: make FirebaseFunctions build for Android

Remove some linkage on Android as the libraries are not present. It is
unclear if this is underlinking, but for now, this allows us to make
progress. Explicitly cast the error value as it is a `DWORD` on Windows
and `CInt` on Unix.

CMakeLists.txt

@@ -209,11 +209,11 @@ target_link_libraries(FirebaseFunctions PUBLIC
   firebase_functions
   FirebaseCore)
 target_link_libraries(FirebaseFunctions PRIVATE
-  crypto
-  firebase_rest_lib
   flatbuffers
-  ssl
+  $<$<PLATFORM_ID:Windows>:crypto>
+  $<$<PLATFORM_ID:Windows>:firebase_rest_lib>
   $<$<PLATFORM_ID:Windows>:libcurl>
+  $<$<PLATFORM_ID:Windows>:ssl>
   $<$<PLATFORM_ID:Windows>:zlibstatic>)
 
 add_library(FirebaseStorage SHARED

Sources/FirebaseFunctions/FunctionsErrorCode.swift

@@ -30,7 +30,7 @@ extension FunctionsErrorCode: RawRepresentable {
 
 extension FunctionsErrorCode {
   init(_ error: firebase.functions.Error, errorMessage: String?) {
-    self.init((code: error.rawValue, message: errorMessage ?? "\(error.rawValue)"))
+    self.init((code: Int32(bitPattern: error.rawValue), message: errorMessage ?? "\(error.rawValue)"))
   }
 
   init?(_ error: firebase.functions.Error?, errorMessage: UnsafePointer<CChar>?) {