stofuse: fix build on Darwin

Author: joonas-fi

pkg/stofuse/collectionadapter.go

@@ -471,7 +471,8 @@ func (a *changedFileInWorkdir) Setattr(ctx context.Context, req *fuse.SetattrReq
 			}
 		}
 
-		existingATime := timespecToTime(existing.Sys().(*syscall.Stat_t).Atim)
+		// some platforms don't support fetching access time.
+		existingATime := accessTimeFromStatt(existing.Sys().(*syscall.Stat_t), existing.ModTime())
 
 		// TODO: use herbis times
 

pkg/stofuse/os_darwin.go

@@ -0,0 +1,13 @@
+package stofuse
+
+// os-specific abstractions (Darwin)
+
+import (
+	"syscall"
+	"time"
+)
+
+// darwin doesn't seem to have field `Atim` in `syscall.Stat_t`
+func accessTimeFromStatt(_ *syscall.Stat_t, modTime time.Time) time.Time {
+	return modTime
+}

pkg/stofuse/os_linux.go

@@ -0,0 +1,12 @@
+package stofuse
+
+// os-specific abstractions (Linux)
+
+import (
+	"syscall"
+	"time"
+)
+
+func accessTimeFromStatt(stat *syscall.Stat_t, _ time.Time) time.Time {
+	return timespecToTime(stat.Atim)
+}