Update check to whether --arch is supported

 dotnet/runtime#116078 --arch was not added until .NET 10 to allow us to skip calling dotnet --info because that is slow, as it is not native code.
        // However, --arch gets ignored if the host does not support it. The output is also identical with or without --arch.
        // After discussion with the runtime team, the best way to determine if the host supports --arch is to call it with an invalid arch to see if it fails, because that only happens when --arch is supported.

        // The --arch flag was added in the middle of .NET 10, so we can assume it is supported if the version is 10.0 or later.
        // We don't want to slow down the current common case for people without .NET 10 by adding another process spawn check.
        // We don't check that the version is 10.0 or later after 2026 when .NET 11 starts rolling out, as It will be slower to check all of the numbers in the output for versions >= 10.

Author: nagilson

vscode-dotnet-runtime-library/src/Acquisition/DotnetConditionValidator.ts

@@ -125,12 +125,14 @@ Please set the PATH to a dotnet host that matches the architecture ${requirement
 
         const findSDKsCommand = CommandExecutor.makeCommand(`"${existingPath}"`, ['--list-sdks', '--arch', requestedArchitecture]);
 
-        const sdkInfo = await (this.executor!).execute(findSDKsCommand, { dotnetInstallToolCacheTtlMs: DOTNET_INFORMATION_CACHE_DURATION_MS }, false).then((result) =>
+        const sdkInfo = await (this.executor!).execute(findSDKsCommand, { dotnetInstallToolCacheTtlMs: DOTNET_INFORMATION_CACHE_DURATION_MS }, false).then(async (result) =>
         {
             if (result.status !== '0')
             {
                 return [];
             }
+
+            const hostSupportsArchFlag = await this.hostSupportsArchFlag(existingPath, result.stdout);
             const sdks = result.stdout.split('\n').map((line) => line.trim()).filter((line) => (line?.length ?? 0) > 0);
             const sdkInfos: IDotnetListInfo[] = sdks.map((sdk) =>
             {
@@ -149,6 +151,22 @@ Please set the PATH to a dotnet host that matches the architecture ${requirement
         return sdkInfo;
     }
 
+    private async hostSupportsArchFlag(dotnetExecutablePath: string, listDotnetInstallsStdout: string): Promise<boolean>
+    {
+        // https://github.com/dotnet/runtime/pull/116078 --arch was not added until .NET 10 to allow us to skip calling dotnet --info because that is slow, as it is not native code.
+        // However, --arch gets ignored if the host does not support it. The output is also identical with or without --arch.
+        // After discussion with the runtime team, the best way to determine if the host supports --arch is to call it with an invalid arch to see if it fails, because that only happens when --arch is supported.
+
+        // The --arch flag was added in the middle of .NET 10, so we can assume it is supported if the version is 10.0 or later.
+        // We don't want to slow down the current common case for people without .NET 10 by adding another process spawn check.
+        // We don't check that the version is 10.0 or later after 2026 when .NET 11 starts rolling out, as It will be slower to check all of the numbers in the output for versions >= 10.
+        const hostMaySupportArchFlag = listDotnetInstallsStdout.includes("10.0") || Date.now() >= new Date('2026-03-01').getTime();
+        // Use runtimes instead of sdks, as sdks will always have a runtime, and runtime search can be cached across both mode calls.
+        const findInvalidCommand = CommandExecutor.makeCommand(`"${dotnetExecutablePath}"`, ['--list-runtimes', '--arch', 'invalid-arch']);
+        const hostSupportsArchFlag = hostMaySupportArchFlag ? (await (this.executor!).execute(findInvalidCommand, { dotnetInstallToolCacheTtlMs: DOTNET_INFORMATION_CACHE_DURATION_MS }, false)).status !== '0' : false;
+        return hostSupportsArchFlag;
+    }
+
     public stringVersionMeetsRequirement(availableVersion: string, requestedVersion: string, requirement: IDotnetFindPathContext): boolean
     {
         const availableMajor = Number(versionUtils.getMajor(availableVersion, this.workerContext.eventStream, this.workerContext));
@@ -298,12 +316,14 @@ Please set the PATH to a dotnet host that matches the architecture ${requirement
         const aspnetCoreString = 'Microsoft.AspNetCore.App';
         const runtimeString = 'Microsoft.NETCore.App';
 
-        const runtimeInfo = await (this.executor!).execute(findRuntimesCommand, { dotnetInstallToolCacheTtlMs: DOTNET_INFORMATION_CACHE_DURATION_MS }, false).then((result) =>
+        const runtimeInfo = await (this.executor!).execute(findRuntimesCommand, { dotnetInstallToolCacheTtlMs: DOTNET_INFORMATION_CACHE_DURATION_MS }, false).then(async (result) =>
         {
             if (result.status !== '0')
             {
                 return [];
             }
+
+            const hostSupportsArchFlag = await this.hostSupportsArchFlag(existingPath, result.stdout);
             const runtimes = result.stdout.split('\n').map((line) => line.trim()).filter((line) => (line?.length ?? 0) > 0);
             const runtimeInfos: IDotnetListInfo[] = runtimes.map((runtime) =>
             {