Exposes sys.Stat_t as a portable alternative to syscall.Stat_t (#1567)

Signed-off-by: Adrian Cole <adrian@tetrate.io>

sys/stat_unsupported.go

@@ -0,0 +1,17 @@
+//go:build (!((amd64 || arm64 || riscv64) && linux) && !((amd64 || arm64) && (darwin || freebsd)) && !((amd64 || arm64) && windows)) || js
+
+package sys
+
+import "io/fs"
+
+// sysParseable is only used here as we define "supported" as being able to
+// parse `info.Sys()`. The above `go:build` constraints exclude 32-bit until
+// that's requested.
+//
+// TODO: When Go 1.21 is out, use the "unix" build constraint (as 1.21 makes
+// our floor Go version 1.19.
+const sysParseable = false
+
+func statFromFileInfo(info fs.FileInfo) Stat_t {
+	return defaultStatFromFileInfo(info)
+}