Disable OpenSSL on Android.

Apparently Android uses BoringSSL, but doesn't actually expose headers
for it in the NDK.

CMakeLists.txt

@@ -63,7 +63,16 @@ option(YUZU_DOWNLOAD_TIME_ZONE_DATA "Always download time zone binaries" OFF)
 
 CMAKE_DEPENDENT_OPTION(YUZU_USE_FASTER_LD "Check if a faster linker is available" ON "NOT WIN32" OFF)
 
-CMAKE_DEPENDENT_OPTION(ENABLE_OPENSSL "Enable OpenSSL backend for ISslConnection" ON "NOT WIN32" OFF)
+set(DEFAULT_ENABLE_OPENSSL ON)
+if (ANDROID OR WIN32)
+    # - Windows defaults to the Schannel backend.
+    # - Android currently has no SSL backend as the NDK doesn't include any SSL
+    #   library; a proper 'native' backend would have to go through Java.
+    # But you can force builds for those platforms to use OpenSSL if you have
+    # your own copy of it.
+    set(DEFAULT_ENABLE_OPENSSL OFF)
+endif()
+option(ENABLE_OPENSSL "Enable OpenSSL backend for ISslConnection" ${DEFAULT_ENABLE_OPENSSL})
 
 # On Android, fetch and compile libcxx before doing anything else
 if (ANDROID)