Enable shared compilation with DOTNET_ROOT fix

Update bxl_rules and bxl_rules_dotnet pins to versions that set
DOTNET_ROOT when shared compilation is enabled. This allows the
VBCSCompiler server to find the correct runtime in the extracted SDK.

Without this fix, VBCSCompiler's apphost inherits the host environment's
DOTNET_ROOT, fails to load the runtime, and each csc invocation wastes
20 seconds on a connection timeout before falling back to in-process.

With the fix: build time drops from ~56 min to ~2 min (with partial
cache), as the persistent compiler server handles all compilations.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: agocke

config.dsc

@@ -21,13 +21,13 @@ config({
                     moduleName: "bxl_rules_repo",
                     owner: "agocke",
                     repository: "bxl_rules",
-                    commit: "931bf68ee4383082c9d41a60e285cb09098c2271",
+                    commit: "3ca4b303bfa7f761544dde16e0234761f457c9ce",
                 },
                 {
                     moduleName: "bxl_rules_dotnet_repo",
                     owner: "agocke",
                     repository: "bxl_rules_dotnet",
-                    commit: "2a84ec46d7a92984fe58529eb57d2d9bb81a2e9c",
+                    commit: "b2219e5a626a802cfbf21058aa94ac8df711259b",
                 },
             ],
         },

src/tests/Common/BUILD.dsc

@@ -17,6 +17,7 @@ export const csharpToolchain = CSharp.csharpToolchainFromContents({
 export const testLibrary = CSharp.csharp_library({
     name: "TestLibrary",
     toolchain: csharpToolchain,
+    useSharedCompilation: true,
     srcs: [
         "CoreCLRTestLibrary/AssertExtensions.cs",
         "CoreCLRTestLibrary/CoreclrTestWrapperLib.cs",
@@ -52,6 +53,7 @@ export const testLibrary = CSharp.csharp_library({
 export const xunitWrapperLibrary = CSharp.csharp_library({
     name: "XUnitWrapperLibrary",
     toolchain: csharpToolchain,
+    useSharedCompilation: true,
     srcs: [
         "XUnitWrapperLibrary/Help.cs",
         "XUnitWrapperLibrary/TestFilter.cs",
@@ -70,6 +72,7 @@ export const xunitWrapperLibrary = CSharp.csharp_library({
 export const xunitWrapperGenerator = CSharp.csharp_library({
     name: "XUnitWrapperGenerator",
     toolchain: csharpToolchain,
+    useSharedCompilation: true,
     srcs: [
         "XUnitWrapperGenerator/CodeBuilder.cs",
         "XUnitWrapperGenerator/Descriptors.cs",

src/tests/coreclr_test/coreclr_test.dsc

@@ -208,6 +208,7 @@ export function coreclr_test(args: CoreClrTestArguments): CoreClrTestResult {
         allowUnsafe: args.allowUnsafe !== undefined ? args.allowUnsafe : true,
         defines: args.defines,
         nowarn: allNowarn,
+        useSharedCompilation: true,
         analyzers: referenceXunitWrapperGenerator ? [Rules.sourceArtifact(Common.xunitWrapperGenerator.binary)] : undefined,
         analyzerConfigs: analyzerConfigs,
     });