Correctly handle calls setting timestamp to 0 (emscripten-core#23310)

If someone calls `utimes("file", 0, 0)` the previous code I wrote would
not adjust the time stamp.

Author: hoodmane

src/library_memfs.js

@@ -172,7 +172,7 @@ addToLibrary({
       },
       setattr(node, attr) {
         for (const key of ["mode", "atime", "mtime", "ctime"]) {
-          if (attr[key]) {
+          if (attr[key] != null) {
             node[key] = attr[key];
           }
         }

src/library_nodefs.js

@@ -166,9 +166,15 @@ addToLibrary({
             // update the common node structure mode as well
             node.mode = attr.mode;
           }
-          if (attr.atime || attr.mtime) {
-            var atime = attr.atime && new Date(attr.atime);
-            var mtime = attr.mtime && new Date(attr.mtime);
+          if (typeof (attr.atime ?? attr.mtime) === "number") {
+            // Unfortunately, we have to stat the current value if we don't want
+            // to change it. On top of that, since the times don't round trip
+            // this will only keep the value nearly unchanged not exactly
+            // unchanged. See:
+            // https://github.com/nodejs/node/issues/56492
+            var stat = () => fs.lstatSync(NODEFS.realPath(node));
+            var atime = new Date(attr.atime ?? stat().atime);
+            var mtime = new Date(attr.mtime ?? stat().mtime);
             fs.utimesSync(path, atime, mtime);
           }
           if (attr.size !== undefined) {

src/library_workerfs.js

@@ -91,7 +91,7 @@ addToLibrary({
       },
       setattr(node, attr) {
         for (const key of ["mode", "atime", "mtime", "ctime"]) {
-          if (attr[key]) {
+          if (attr[key] != null) {
             node[key] = attr[key];
           }
         }

test/other/codesize/test_codesize_cxx_ctors1.gzsize

@@ -1 +1 @@
-8332
+8335

test/other/codesize/test_codesize_cxx_ctors1.jssize

@@ -1 +1 @@
-20255
+20261

test/other/codesize/test_codesize_cxx_ctors2.gzsize

@@ -1 +1 @@
-8314
+8317

test/other/codesize/test_codesize_cxx_ctors2.jssize

@@ -1 +1 @@
-20223
+20229

test/other/codesize/test_codesize_cxx_except.gzsize

@@ -1 +1 @@
-9336
+9339

test/other/codesize/test_codesize_cxx_except.jssize

@@ -1 +1 @@
-24023
+24029

test/other/codesize/test_codesize_cxx_except_wasm.gzsize

@@ -1 +1 @@
-8280
+8283