Fix: Could not find extension target platform

[steel97]

Latest version of extension will throw error shown below, if package published with:

npx gulp 'vsix:release:neutral'

Reason is that neutral build doesn't contains TargetPlatform in vsixmanifest, which is required here:

free-vscode-csharp/src/lsptoolshost/dotnetRuntimeExtensionResolver.ts

Lines 153 to 157 in 2dea855

	const contents = await readFile(vsixManifestFile, 'utf-8');
	const targetPlatformMatch = /TargetPlatform="(.*)"/.exec(contents);
	if (!targetPlatformMatch) {
	throw new Error(`Could not find extension target platform in ${vsixManifestFile}`);
	}

Suggested solution is to return undefined instead of throwing error, in that case proccess.arch will be used:

free-vscode-csharp/src/lsptoolshost/dotnetRuntimeExtensionResolver.ts

Line 44 in 2dea855

const extensionArchitecture = (await this.getArchitectureFromTargetPlatform()) ?? process.arch;

Tested on: VSCodium 1.96.4, windows 11

Upd: also tested on macos (arm), same VSCodium version