test: add wasi test for symlink() and readlink()

This test provides missing coverage for __wasi_path_symlink()
and __wasi_path_readlink().

PR-URL: #31403
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/wasi/c/create_symlink.c

@@ -0,0 +1,26 @@
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+int main() {
+  const char* target = "./input.txt";
+  const char* linkpath = "/sandbox/subdir/test_link";
+  char readlink_result[128];
+  size_t result_size = sizeof(readlink_result);
+
+  assert(0 == symlink(target, linkpath));
+  assert(readlink(linkpath, readlink_result, result_size) ==
+         strlen(target) + 1);
+  assert(0 == strcmp(readlink_result, target));
+
+  FILE* file = fopen(linkpath, "r");
+  assert(file != NULL);
+
+  int c = fgetc(file);
+  while (c != EOF) {
+    int wrote = fputc(c, stdout);
+    assert(wrote != EOF);
+    c = fgetc(file);
+  }
+}

test/wasi/test-wasi-symlinks.js

@@ -74,6 +74,7 @@ if (process.argv[2] === 'wasi-child') {
     assert.strictEqual(child.stdout.toString(), options.stdout || '');
   }
 
+  runWASI({ test: 'create_symlink', stdout: 'hello from input.txt' });
   runWASI({ test: 'follow_symlink', stdout: 'hello from input.txt' });
   runWASI({ test: 'symlink_escape' });
   runWASI({ test: 'symlink_loop' });