Fix Linux pipeline

Author: RiRiSharp

build.sh

@@ -20,6 +20,8 @@ DRYRUN=
 SHOW_VERSION=false
 SCRIPT_ARGUMENTS=()
 
+sudo apt install mono-devel # ubuntu-latest does not come with mono pre-installed anymore.
+
 # Parse arguments.
 for i in "$@"; do
     case $1 in