Added basic support for FreeBSD.

Freebsd-support: Change bash shebang to use /usr/bin/env

Freebsd-support: Fix go vet "undefined" fixes when running make ci

freebsd: stub xattr functions

/proc/PID/fd does not exist on freebsd.

freebsd-support: modify FchmodatNofollow for FreeBSD

FreeBSD supports the Fchmodat system call, with the AT_SYMLINK_NOFOLLOW
flag. FchmodatNofollow has been modified to use this system call and
flag.

freebsd-support: PR changes and fixes

* Functions in fusefrontend_reverse/node_xattr_freebsd.go have been
  stubbed for now.

* asuser_freebsd.go updated to only run f() when context is nil;
  otherwise log a warning and return an error.

* emulate.go build flags updated, and FreeBSD specific version added.

* sys_freebsd.go bug in Renameat2 with RENAME_EXCHANGE flag fixed.
  FreeBSD does not support atomic file swapping, so this flag now
  returns an error.

* unix2syscall and atime is identical between FreeBSD and Darwin,
  updated filenames so Go will build the file for FreeBSD and Mac OS.

freebsd-support: Addressed more PR comments and fixed build tags

1 files changed, 28 insertions, 0 deletions

diff --git a/internal/syscallcompat/unix2syscall.go b/internal/syscallcompat/unix2syscall.go
new file mode 100644
index 0000000..fa2e8c4
--- /dev/null
+++ b/internal/syscallcompat/unix2syscall.go
@@ -0,0 +1,28 @@
+//go:build darwin || freebsd
+
+package syscallcompat
+
+import (
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+// Unix2syscall converts a unix.Stat_t struct to a syscall.Stat_t struct.
+func Unix2syscall(u unix.Stat_t) syscall.Stat_t {
+	return syscall.Stat_t{
+		Dev:       u.Dev,
+		Ino:       u.Ino,
+		Nlink:     u.Nlink,
+		Mode:      u.Mode,
+		Uid:       u.Uid,
+		Gid:       u.Gid,
+		Rdev:      u.Rdev,
+		Size:      u.Size,
+		Blksize:   u.Blksize,
+		Blocks:    u.Blocks,
+		Atimespec: syscall.Timespec(u.Atim),
+		Mtimespec: syscall.Timespec(u.Mtim),
+		Ctimespec: syscall.Timespec(u.Ctim),
+	}
+}