For Travis CI - disable Mach-O universal binary build for 64-bit iOS.

When Travis CI is overloaded, the CI builds tend to get longer. Our iOS 32-bit and 64-bit CI build are usually finished very close to the 50 minutes time limit but may overshoot to pass the limit when Travis CI is overloaded. Using the xcpretty only helps in reducing the log size but it cannot help in this case. This commit disables again the universal binary build for the 64-bit iOS build when packaging the build artifact. The Mach-O universal binary build for 32-bit iOS build may be disabled too in the near future when we get more samples or the overloaded situation gets worse.

Rakefile

@@ -160,9 +160,11 @@ task :ci_package_upload do
   end
   # Make the package
   if ENV['IOS']
-    # Build Mach-O universal binary consisting of iphoneos (universal ARM archs including 'arm64' if 64-bit is enabled) and iphonesimulator (i386 arch and also x86_64 arch if 64-bit is enabled)
-    system 'echo Rebuild Urho3D library as Mach-O universal binary'
-    xcode_build(0, "#{platform_prefix}Build/Urho3D.xcodeproj", 'Urho3D_universal') or abort 'Failed to build Mach-O universal binary'
+    if ENV['CI'] && ENV['URHO3D_64BIT'].to_i == 0  # Skip Mach-O universal binary build for 64-bit build for the time being as otherwise overall build time may exceed 50 minutes time limit when Travis-CI is being overloaded
+      # Build Mach-O universal binary consisting of iphoneos (universal ARM archs including 'arm64' if 64-bit is enabled) and iphonesimulator (i386 arch and also x86_64 arch if 64-bit is enabled)
+      system 'echo Rebuild Urho3D library as Mach-O universal binary'
+      xcode_build(0, "#{platform_prefix}Build/Urho3D.xcodeproj", 'Urho3D_universal') or abort 'Failed to build Mach-O universal binary'
+    end
     # There is a bug in CMake/CPack that causes the 'package' target failed to build for IOS platform, workaround by calling cpack directly
     system "cd #{platform_prefix}Build && cpack -G TGZ 2>/dev/null" or abort 'Failed to make binary package'
   elsif ENV['XCODE']