Alpine linux libc.musl build error fix

Prevent build error on Alpine Linux host:
libfakeroot.c error: conflicting types for 'id_t'
Error relocating librecmc/staging_dir/host/lib/libfakeroot.so: SEND_GET_XATTR: symbol not found

--- a/libfakeroot.c
+++ b/libfakeroot.c
@@ -86,12 +86,14 @@
 #define SEND_STAT64(a,b,c) send_stat64(a,b,c)
 #define SEND_GET_STAT(a,b) send_get_stat(a,b)
 #define SEND_GET_STAT64(a,b) send_get_stat64(a,b)
+#define SEND_GET_XATTR(a,b,c) send_get_xattr(a,b,c)
 #define SEND_GET_XATTR64(a,b,c) send_get_xattr64(a,b,c)
 #else
 #define SEND_STAT(a,b,c) send_stat(a,b)
 #define SEND_STAT64(a,b,c) send_stat64(a,b)
 #define SEND_GET_STAT(a,b) send_get_stat(a)
 #define SEND_GET_STAT64(a,b) send_get_stat64(a)
+#define SEND_GET_XATTR(a,b,c) send_get_xattr(a,b)
 #define SEND_GET_XATTR64(a,b,c) send_get_xattr64(a,b)
 #endif
 
@@ -142,8 +144,9 @@
 
 /* 10.10 uses id_t in getpriority/setpriority calls, so pretend
    id_t is used everywhere, just happens to be int on some OSes */
-#ifndef _ID_T
+#if !defined(_ID_T) && !defined(__DEFINED_id_t)
 #define _ID_T
+#define __DEFINED_id_t
 typedef int id_t;
 #endif
 #endif