download PermissionDenied. make file writable after copy to cache

Lines 255 to 259 in 7e85fa9

    
           case "file:": { 
        
             console.log(`${colors.green("Copying")} ${url}`); 
        
             await Deno.copyFile(fromFileUrl(url), cacheFilePath); 
        
             break; 
        
           }

when the source file is read-only (chmod 0555)
then the cached file is also read-only

future calls to download fail
because the target file in cache is read-only

first call:

Copying file:///tmp/tmp.aGowOqCn9e/vscode/vscode-deno/libwebview.so

second call:

Copying file:///tmp/tmp.aGowOqCn9e/vscode/vscode-deno/libwebview.so
error: Uncaught (in promise) PermissionDenied: Permission denied (os error 13), copy '/tmp/tmp.aGowOqCn9e/vscode/vscode-deno/libwebview.so' -> '/home/user/.cache/deno/plug/file/a8eb18dc8f0f8199d82db2f57b5f04a3f527e44095eca509c3960f4760b36e4e.so'
        await Deno.copyFile(fromFileUrl(url), cacheFilePath);
        ^
    at async Object.copyFile (deno:runtime/js/30_fs.js:64:5)
    at async download (https://deno.land/x/plug@1.0.0-rc.3/download.ts:257:9)
    at async dlopen (https://deno.land/x/plug@1.0.0-rc.3/mod.ts:145:22)
    at async file:///tmp/tmp.aGowOqCn9e/vscode/vscode-deno/webview_deno/src/ffi.ts:154:20

called from https://deno.land/x/webview

discuss: should preserve the execution bit of the original file? or just chmod 0644 all files?

      case "file:": {
        console.log(`${colors.green("Copying")} ${url}`);
        /*
        // Deno.chmod currently throws on Windows
        await Deno.copyFile(fromFileUrl(url), cacheFilePath);
        await Deno.chmod(cacheFilePath, 0o644);
        */
        // portable workaround
        // note: this is limited by memory size
        // todo: copy large file in chunks
        const data = await Deno.readFile(fromFileUrl(url));
        await Deno.writeFile(cacheFilePath, data);
        break;
      }

merged in https://github.com/milahu/plug

Interesting, I will look into this later but I think the easiest solution is just to do chmod 0o644 on posix.

	case "file:": {
	console.log(`${colors.green("Copying")} ${url}`);
	await Deno.copyFile(fromFileUrl(url), cacheFilePath);
	break;
	}