src/vs/base/node/powershell.ts/PossiblePowerShellExe/exists
class PossiblePowerShellExe:	public async exists(): Promise<boolean> {
		if (this.knownToExist === undefined) {
			this.knownToExist = await pfs.SymlinkSupport.existsFile(this.exePath);
		}
		return this.knownToExist;
	}