Update build commands to ensure minimum .NET SDK is 9

Author: bradwilson

build

@@ -19,7 +19,7 @@ else
 	guard_bin mono "please install Mono from https://www.mono-project.com/"
 fi
 
-[ $(dotnet --version | cut -d. -f1) -ge 8 ] || write_error ".NET SDK version $(dotnet --version) is too low; please install version 8.0 or later from https://dot.net/"
+[ $(dotnet --version | cut -d. -f1) -ge 9 ] || write_error ".NET SDK version $(dotnet --version) is too low; please install version 9.0 or later from https://dot.net/"
 
 git submodule status | while read line; do
 	if [ "$(echo $line | cut -b1)" == "-" ]; then

build.ps1

@@ -21,8 +21,8 @@ if ($null -eq (Get-Command "dotnet" -ErrorAction Ignore)) {
 }
 
 $version = [Version]$([regex]::matches((&dotnet --version), '^(\d+\.)?(\d+\.)?(\*|\d+)').value)
-if ($version.Major -lt 8) {
-	throw ".NET SDK version ($version) is too low; please install version 8.0 or later"
+if ($version.Major -lt 9) {
+	throw ".NET SDK version ($version) is too low; please install version 9.0 or later"
 }
 
 if ($null -eq (Get-Command "msbuild.exe" -ErrorAction Ignore)) {