Update workspace settings to use modern build system. Update Podfile to strip VALID_ARCHS flag from generated target xcconfig (deprecated in Xcode 12)

Podfile

@@ -109,6 +109,7 @@ post_install do |installer|
   configure_testable_build(installer)
   disable_bitcode(installer)
   disable_armv7(installer)
+  strip_valid_archs(installer)
   disable_non_development_pod_warnings(installer)
   copy_acknowledgements
 end
@@ -192,6 +193,15 @@ def disable_armv7(installer)
   end
 end
 
+def strip_valid_archs(installer)
+  Dir.glob('Pods/Target Support Files/**/*.xcconfig') do |xcconfig_path|
+    xcconfig = File.read(xcconfig_path)
+    xcconfig_mod = xcconfig.gsub('VALID_ARCHS[sdk=iphoneos*] = arm64', '')
+    xcconfig_mod = xcconfig_mod.gsub('VALID_ARCHS[sdk=iphonesimulator*] = x86_64', '')
+    File.open(xcconfig_path, "w") { |file| file << xcconfig_mod }
+  end
+end
+
 # Disable warnings on any Pod not currently being modified
 def disable_non_development_pod_warnings(installer)
   non_development_targets = installer.pod_targets.select do |target|

Signal.xcworkspace/xcshareddata/WorkspaceSettings.xcsettings

@@ -2,8 +2,6 @@
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
-	<key>BuildSystemType</key>
-	<string>Original</string>
 	<key>PreviewsEnabled</key>
 	<false/>
 </dict>