Non-SFI mode: Implement test launcher for nacl_helper_nonsfi_unittests.

This CL implements a test launcher customized for nacl_helper_nonsfi_unittests.
- Existing nacl_helper_nonsfi_unittests is renamed to nacl_helper_nonsfi_unittests_main.
- The new test launcher is built with a toolchain for the target architecture rather than PNaCl toolchain.
- XmlUnitTestResultPrinter is now extracted into a separate file.

TEST=Ran bots (with and without editing testing/buildbots scripts). Run locally.
BUG=358465

Review URL: https://codereview.chromium.org/1154313003

Cr-Commit-Position: refs/heads/master@{#333430}


CrOS-Libchrome-Original-Commit: 8fc7c823b9dd2b7890c96438f347383aa713c1d6
diff --git a/base/files/file_util_posix.cc b/base/files/file_util_posix.cc
index b4a64ba..a8c5d44 100644
--- a/base/files/file_util_posix.cc
+++ b/base/files/file_util_posix.cc
@@ -651,6 +651,7 @@
   results->FromStat(file_info);
   return true;
 }
+#endif  // !defined(OS_NACL_NONSFI)
 
 FILE* OpenFile(const FilePath& filename, const char* mode) {
   ThreadRestrictions::AssertIOAllowed();
@@ -710,6 +711,8 @@
   return true;
 }
 
+#if !defined(OS_NACL_NONSFI)
+
 bool AppendToFile(const FilePath& filename, const char* data, int size) {
   ThreadRestrictions::AssertIOAllowed();
   bool ret = true;