[NaCl SDK] nacl_io: Make IRT intercepts (and their test code) more robust.

native_client_sdk/src/tests/nacl_io_test/kernel_wrap_test.cc

Index: native_client_sdk/src/tests/nacl_io_test/kernel_wrap_test.cc
diff --git a/native_client_sdk/src/tests/nacl_io_test/kernel_wrap_test.cc b/native_client_sdk/src/tests/nacl_io_test/kernel_wrap_test.cc
index bbfa60047a31cc9bbb6afc3d3891f9b91308bd00..764c247e649c8a6c5d11ea129e46d9765f74e436 100644
--- a/native_client_sdk/src/tests/nacl_io_test/kernel_wrap_test.cc
+++ b/native_client_sdk/src/tests/nacl_io_test/kernel_wrap_test.cc
@@ -109,6 +109,10 @@ class KernelWrapTest : public ::testing::Test {
   KernelWrapTest() {}
 
   virtual void SetUp() {
+    // Initialize the global errno value to a consistent value rather than
+    // relying on its value from previous test runs.
+    errno = 0;
+
     // Initializing the KernelProxy opens stdin/stdout/stderr.
     EXPECT_CALL(mock, open(_, _))
         .WillOnce(Return(0))