Remove usage of wslu

This PR is simplified version of #198 - Windows 10 does not allow
installing the OS to locations other than C:\Windows so fetching
%systemroot% is unnecessary here (and since WSL is exclusive to
Windows 10, we do not need to worry about Win7 here). WSL also handles
marshaling paths between WSL and Windows, so we don't need to convert
this path manually.

index.js

@@ -7,30 +7,10 @@ const isWsl = require('is-wsl');
 const isDocker = require('is-docker');
 
 const pAccess = promisify(fs.access);
-const pExecFile = promisify(childProcess.execFile);
 
 // Path to included `xdg-open`.
 const localXdgOpenPath = path.join(__dirname, 'xdg-open');
 
-// Convert a path from WSL format to Windows format:
-// `/mnt/c/Program Files/Example/MyApp.exe` → `C:\Program Files\Example\MyApp.exe`
-const wslToWindowsPath = async path => {
-	const {stdout} = await pExecFile('wslpath', ['-w', path]);
-	return stdout.trim();
-};
-
-// Convert a path from Windows format to WSL format
-const windowsToWslPath = async path => {
-	const {stdout} = await pExecFile('wslpath', [path]);
-	return stdout.trim();
-};
-
-// Get an environment variable from Windows
-const wslGetWindowsEnvVar = async envVar => {
-	const {stdout} = await pExecFile('wslvar', [envVar]);
-	return stdout.trim();
-};
-
 module.exports = async (target, options) => {
 	if (typeof target !== 'string') {
 		throw new TypeError('Expected a `target`');
@@ -69,8 +49,10 @@ module.exports = async (target, options) => {
 			cliArguments.push('-a', app);
 		}
 	} else if (process.platform === 'win32' || (isWsl && !isDocker())) {
-		const windowsRoot = isWsl ? await wslGetWindowsEnvVar('systemroot') : process.env.SYSTEMROOT;
-		command = String.raw`${windowsRoot}\System32\WindowsPowerShell\v1.0\powershell${isWsl ? '.exe' : ''}`;
+		command = isWsl ?
+			'/mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe' :
+			`${process.env.SYSTEMROOT}\\System32\\WindowsPowerShell\\v1.0\\powershell`;
+
 		cliArguments.push(
 			'-NoProfile',
 			'-NonInteractive',
@@ -79,9 +61,7 @@ module.exports = async (target, options) => {
 			'-EncodedCommand'
 		);
 
-		if (isWsl) {
-			command = await windowsToWslPath(command);
-		} else {
+		if (!isWsl) {
 			childProcessOptions.windowsVerbatimArguments = true;
 		}
 
@@ -92,11 +72,6 @@ module.exports = async (target, options) => {
 		}
 
 		if (app) {
-			if (isWsl && app.startsWith('/')) {
-				const windowsPath = await wslToWindowsPath(app);
-				app = windowsPath;
-			}
-
 			// Double quote with double quotes to ensure the inner quotes are passed through.
 			// Inner quotes are delimited for PowerShell interpretation with backticks.
 			encodedArguments.push(`"\`"${app}\`""`, '-ArgumentList');