Trying to create a directory in a file should return ENOTDIR not EPERM

src/library_fs.js

@@ -372,6 +372,9 @@ FS.staticInit();
       return 0;
     },
     mayCreate(dir, name) {
+      if (!FS.isDir(dir.mode)) {
+        return {{{ cDefs.ENOTDIR }}};
+      }
       try {
         var node = FS.lookupNode(dir, name);
         return {{{ cDefs.EEXIST }}};

test/fs/test_enotdir.c

@@ -0,0 +1,17 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+
+int main() {
+    {
+        int src_fd = open("file", O_CREAT | O_WRONLY, 0777);
+        close(src_fd);
+    }
+    {
+        int target_fd = mkdir("file/blah", 0777);
+        printf("target_fd: %d, errno: %d %s\n", target_fd, errno, strerror(errno));
+    }
+}

test/fs/test_enotdir.out

@@ -0,0 +1 @@
+target_fd: -1, errno: 54 Not a directory

test/test_core.py

@@ -5822,6 +5822,10 @@ def test_fs_write(self):
   def test_fs_emptyPath(self):
     self.do_run_in_out_file_test('fs/test_emptyPath.c')
 
+  @also_with_noderawfs
+  def test_fs_enotdir(self):
+    self.do_run_in_out_file_test('fs/test_enotdir.c')
+
   @also_with_noderawfs
   def test_fs_append(self):
     self.do_runf('fs/test_append.c', 'success')