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

5 files changed, 15 insertions, 5 deletions

diff --git a/profiling/ls.bash b/profiling/ls.bash
index 35f5a39..334d8be 100755
--- a/profiling/ls.bash
+++ b/profiling/ls.bash
@@ -1,4 +1,6 @@
-#!/bin/bash -eu
+#!/usr/bin/env bash
+
+set -eu
 
 cd "$(dirname "$0")"
 
diff --git a/profiling/streaming-read.bash b/profiling/streaming-read.bash
index 86ef942..138148c 100755
--- a/profiling/streaming-read.bash
+++ b/profiling/streaming-read.bash
@@ -1,4 +1,6 @@
-#!/bin/bash -eu
+#!/usr/bin/env bash
+
+set -eu
 
 cd "$(dirname "$0")"
 
diff --git a/profiling/streaming-write.bash b/profiling/streaming-write.bash
index 6f3af56..3c29ee6 100755
--- a/profiling/streaming-write.bash
+++ b/profiling/streaming-write.bash
@@ -1,4 +1,6 @@
-#!/bin/bash -eu
+#!/usr/bin/env bash
+
+set -eu
 
 cd "$(dirname "$0")"
 
diff --git a/profiling/tar-extract.bash b/profiling/tar-extract.bash
index f176368..e98100a 100755
--- a/profiling/tar-extract.bash
+++ b/profiling/tar-extract.bash
@@ -1,4 +1,6 @@
-#!/bin/bash -eu
+#!/usr/bin/env bash
+
+set -eu
 
 cd "$(dirname "$0")"
 
diff --git a/profiling/write-trace.bash b/profiling/write-trace.bash
index 31af492..8b7cec9 100755
--- a/profiling/write-trace.bash
+++ b/profiling/write-trace.bash
@@ -1,8 +1,10 @@
-#!/bin/bash -eu
+#!/usr/bin/env bash
 #
 # Write an execution trace of writing 100MB of data
 # to a new gocryptfs mount on /tmp
 
+set -eu
+
 cd "$(dirname "$0")"
 
 T=$(mktemp -d)