Build for .NET 9 too, fix build error

Author: Sergio0694

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "8.0.100",
+    "version": "9.0.100",
     "rollForward": "latestFeature"
   }
 }

nuget/SQLite-net-base/SQLite-net-base.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net8.0;net9.0</TargetFrameworks>
     <AssemblyName>SQLite-net</AssemblyName>
     <PackageId>sqlite-net-base</PackageId>
     <AssemblyTitle>SQLite-net .NET Standard Base Library</AssemblyTitle>

nuget/SQLite-net-sqlcipher/SQLite-net-sqlcipher.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net8.0;net9.0</TargetFrameworks>
     <AssemblyName>SQLite-net</AssemblyName>
     <PackageId>sqlite-net-sqlcipher</PackageId>
     <AssemblyTitle>SQLite-net SQLCipher .NET Standard Library</AssemblyTitle>

nuget/SQLite-net-static/SQLite-net-static.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net8.0;net9.0</TargetFrameworks>
     <AssemblyName>SQLite-net</AssemblyName>
     <PackageId>sqlite-net-static</PackageId>
     <AssemblyTitle>SQLite-net .NET Standard P/Invoke Library</AssemblyTitle>

nuget/SQLite-net-std/SQLite-net-std.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net8.0;net9.0</TargetFrameworks>
     <AssemblyName>SQLite-net</AssemblyName>
     <PackageId>sqlite-net-pcl</PackageId>
     <AssemblyTitle>SQLite-net Official .NET Standard Library</AssemblyTitle>

src/SQLite.cs

@@ -1880,7 +1880,7 @@ void DoSavePointExecute (string savepoint, string cmd)
 				if (Int32.TryParse (savepoint.Substring (firstLen + 1), out depth)) {
 					// TODO: Mild race here, but inescapable without locking almost everywhere.
 					if (0 <= depth && depth < _transactionDepth) {
-#if NETFX_CORE || USE_SQLITEPCL_RAW || NETCORE
+#if NETFX_CORE || USE_SQLITEPCL_RAW || NETCORE || NET8_0_OR_GREATER
 						Volatile.Write (ref _transactionDepth, depth);
 #elif SILVERLIGHT
 						_transactionDepth = depth;