Add wcsftime from musl. NFC (#23061)

See #23045

Author: sbc100

test/other/test_wcsftime.c

@@ -0,0 +1,37 @@
+// Copyright 2017 The Emscripten Authors.  All rights reserved.
+// Emscripten is available under two separate licenses, the MIT license and the
+// University of Illinois/NCSA Open Source License.  Both these licenses can be
+// found in the LICENSE file.
+
+#include <assert.h>
+#include <time.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <wchar.h>
+
+int main() {
+  struct tm tm;
+  wchar_t s[1000];
+
+  // Ensure all fields of `tm` are initialized correctly
+  // before we start messing with them.
+  time_t t = 0;
+  gmtime_r(&t, &tm);
+
+  tm.tm_sec = 4;
+  tm.tm_min = 23;
+  tm.tm_hour = 20;
+  tm.tm_mday = 21;
+  tm.tm_mon = 1;
+  tm.tm_year = 74;
+  tm.tm_wday = 4;
+  tm.tm_yday = 51;
+  tm.tm_isdst = 0;
+
+  const wchar_t *fmt = L"%m/%d/%Y %H:%M:%S %Z";
+  wcsftime(s, sizeof(s), fmt, &tm);
+  printf("%ls -> %ls\n", fmt, s);
+
+  return 0;
+}

test/other/test_wcsftime.out

@@ -0,0 +1 @@
+%m/%d/%Y %H:%M:%S %Z -> 02/21/1974 20:23:04 GMT

test/test_other.py

@@ -6193,6 +6193,10 @@ def test_strptime_reentrant(self):
   def test_strftime(self):
     self.do_other_test('test_strftime.c')
 
+  @crossplatform
+  def test_wcsftime(self):
+    self.do_other_test('test_wcsftime.c')
+
   @crossplatform
   def test_strftime_zZ(self):
     if MACOS:

tools/system_libs.py

@@ -1233,7 +1233,9 @@ def get_files(self):
           '__tm_to_secs.c',
           '__year_to_secs.c',
           '__month_to_secs.c',
+          'wcsftime.c',
         ])
+
     libc_files += files_in_path(
         path='system/lib/libc/musl/src/legacy',
         filenames=['getpagesize.c', 'err.c', 'euidaccess.c'])