Fix build with musl libc

* resource.c: Include <sys/sysinfo.h> for struct sysinfo definition.

Reported-by: Steven Honeyman <stevenhoneyman@gmail.com>
diff --git a/resource.c b/resource.c
index 12e218f..8054c7b 100644
--- a/resource.c
+++ b/resource.c
@@ -302,6 +302,8 @@
 }
 #endif /* ALPHA */
 
+#include <sys/sysinfo.h>
+
 int
 sys_sysinfo(struct tcb *tcp)
 {