Auto merge of #2988 - SteveLauC:XATTR-constants-on-NetBSD, r=JohnTitor

add extended attributes constants on NetBSD

Add three EA-related constants on NetBSD:
1. [XATTR_CREATE](https://github.com/NetBSD/src/blob/ac36f3f9fee8aff1c69d653503149faaa531f752/sys/sys/xattr.h#L54)
2. [XATTR_REPLACE](https://github.com/NetBSD/src/blob/ac36f3f9fee8aff1c69d653503149faaa531f752/sys/sys/xattr.h#L55)
3. [EXTATTR_NAMESPACE_EMPTY](https://github.com/NetBSD/src/blob/ac36f3f9fee8aff1c69d653503149faaa531f752/sys/sys/extattr.h#L44)

And include `sys/xattr.h` in the test.

Author: bors

libc-test/build.rs

@@ -1038,6 +1038,7 @@ fn test_netbsd(target: &str) {
         "string.h",
         "sys/endian.h",
         "sys/exec_elf.h",
+        "sys/xattr.h",
         "sys/extattr.h",
         "sys/file.h",
         "sys/ioctl.h",

libc-test/semver/netbsd.txt

@@ -1534,4 +1534,7 @@ vm_size_t
 wait4
 waitid
 dirname
-basename
+basename
+XATTR_CREATE
+XATTR_REPLACE
+EXTATTR_NAMESPACE_EMPTY

src/unix/bsd/netbsdlike/netbsd/mod.rs

@@ -2315,6 +2315,12 @@ pub const _REG_RFLAGS: ::c_int = 23;
 pub const _REG_RSP: ::c_int = 24;
 pub const _REG_SS: ::c_int = 25;
 
+// sys/xattr.h
+pub const XATTR_CREATE: ::c_int = 0x01;
+pub const XATTR_REPLACE: ::c_int = 0x02;
+// sys/extattr.h
+pub const EXTATTR_NAMESPACE_EMPTY: ::c_int = 0;
+
 const_fn! {
     {const} fn _ALIGN(p: usize) -> usize {
         (p + _ALIGNBYTES) & !_ALIGNBYTES