Remove TimeValue usage from FileSpec.h

Summary:
The only usage there was in GetModificationTime(). I also took the opportunity
to move this function from FileSpec to the FileSystem class - since we are
using FileSpecs to also represent remote files for which we cannot (easily)
retrieve modification time, it makes sense to make the decision to get the
modification time more explicit.

The new function returns a llvm::sys::TimePoint<>. To aid the transition
from TimeValue, I have added a constructor to it which enables implicit
conversion from a time_point.

Reviewers: zturner, clayborg

Subscribers: mehdi_amini, tberghammer, danalbert, beanz, mgorny, lldb-commits

Differential Revision: https://reviews.llvm.org/D25392

llvm-svn: 285702
diff --git a/lldb/source/Plugins/ObjectContainer/BSD-Archive/ObjectContainerBSDArchive.cpp b/lldb/source/Plugins/ObjectContainer/BSD-Archive/ObjectContainerBSDArchive.cpp
index 90213ba..18f9316 100644
--- a/lldb/source/Plugins/ObjectContainer/BSD-Archive/ObjectContainerBSDArchive.cpp
+++ b/lldb/source/Plugins/ObjectContainer/BSD-Archive/ObjectContainerBSDArchive.cpp
@@ -34,6 +34,7 @@
 #include "lldb/Core/PluginManager.h"
 #include "lldb/Core/Stream.h"
 #include "lldb/Core/Timer.h"
+#include "lldb/Host/FileSystem.h"
 #include "lldb/Symbol/ObjectFile.h"
 
 using namespace lldb;
@@ -452,7 +453,7 @@
   data.SetData(data_sp, data_offset, data_sp->GetByteSize());
   if (file && data_sp && ObjectContainerBSDArchive::MagicBytesMatch(data)) {
     const size_t initial_count = specs.GetSize();
-    TimeValue file_mod_time = file.GetModificationTime();
+    TimeValue file_mod_time = FileSystem::GetModificationTime(file);
     Archive::shared_ptr archive_sp(Archive::FindCachedArchive(
         file, ArchSpec(), file_mod_time, file_offset));
     bool set_archive_arch = false;