Enable syscall_test on windows.

tests/syscalls/syscalls.cc

Index: tests/syscalls/syscalls.cc
diff --git a/tests/syscalls/syscalls.cc b/tests/syscalls/syscalls.cc
index 2ff8c153e7df0e043a5d5f2445afed9b06a343ff..cc17f76bb226b2819a5f7695746e4bb7faef1cab 100644
--- a/tests/syscalls/syscalls.cc
+++ b/tests/syscalls/syscalls.cc
@@ -174,7 +174,12 @@ bool test_getcwd() {
 
   // Calculate parent folder.
   strncpy(parent, dirname, PATH_MAX);
-  strrchr(parent, '/')[0] = '\0';
+  char *basename_start = strrchr(parent, '/');
+  if (basename_start == NULL) {
+    basename_start = strrchr(parent, '\\');
+    ASSERT_NE_MSG(basename_start, NULL, "test_file contains no dir seperator");
+  }
+  basename_start[0] = '\0';
 
   int retcode = chdir("..");
   ASSERT_EQ_MSG(retcode, 0, "chdir() failed");