Update the version of Mono used for builds (CI)

Signed-off-by: Dimitar Dobrev <[email protected]>

Author: ddobrev

build/InstallMono.sh

@@ -1,11 +1,12 @@
 OS=$(uname -s)
 if [ "$OS" == "Darwin" ]; then
-	wget -O mono.pkg https://download.mono-project.com/archive/5.18.0/macos-10-universal/MonoFramework-MDK-5.18.0.240.macos10.xamarin.universal.pkg
+	wget -O mono.pkg https://download.mono-project.com/archive/6.10.0/macos-10-universal/MonoFramework-MDK-6.10.0.macos10.xamarin.universal.pkg
 	sudo installer -pkg mono.pkg -target /
 	export PATH=$PATH:/Library/Frameworks/Mono.framework/Versions/Current/bin
 elif [ "$OS" == "Linux" ]; then
+	sudo apt install gnupg ca-certificates
 	sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
-	echo "deb http://download.mono-project.com/repo/debian wheezy main" | sudo tee /etc/apt/sources.list.d/mono-xamarin.list
+	echo "deb https://download.mono-project.com/repo/ubuntu stable-bionic main" | sudo tee /etc/apt/sources.list.d/mono-official-stable.list
 	sudo apt-get update -qq
 	sudo apt-get install -y --force-yes mono-mcs libmono-system-runtime4.0-cil
 fi