autofs-5.1.8 - define fallback dummy NSS config path

From: Sam James <sam@gentoo.org>

On musl, _PATH_NSSWITCH_CONF won't be defined (it doesn't support NSS),
so let's give it a dummy path when it's not defined by glibc.

Fixes build failures like:
```
../include/nsswitch.h:27:23: error: '_PATH_NSSWITCH_CONF' undeclared (first use in this function)
   27 | #define NSSWITCH_FILE _PATH_NSSWITCH_CONF
      |                       ^~~~~~~~~~~~~~~~~~~
```

Tested-by: Yixun Lan <dlan@gentoo.org>
Signed-off-by: Sam James <sam@gentoo.org>
---
 CHANGELOG          |    1 +
 include/nsswitch.h |    4 ++++
 2 files changed, 5 insertions(+)

diff --git a/CHANGELOG b/CHANGELOG
index 53b487eb..0627db48 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -19,6 +19,7 @@
 - dont use initgroups() at spawn.
 - fix bashism in configure.
 - musl: fix missing include in hash.h.
+- musl: define fallback dummy NSS config path
 
 19/10/2021 autofs-5.1.8
 - add xdr_exports().
diff --git a/include/nsswitch.h b/include/nsswitch.h
index d3e40277..8376113e 100644
--- a/include/nsswitch.h
+++ b/include/nsswitch.h
@@ -24,6 +24,10 @@
 #include <netdb.h>
 #include "list.h"
 
+#ifndef _PATH_NSSWITCH_CONF
+#define _PATH_NSSWITCH_CONF "/dev/null"
+#endif
+
 #define NSSWITCH_FILE _PATH_NSSWITCH_CONF
 
 enum nsswitch_status {