Add kvm.h into freebsd header list

Author: GuillaumeGomez

libc-test/build.rs

@@ -1774,6 +1774,7 @@ fn test_freebsd(target: &str) {
                 "grp.h",
                 "iconv.h",
                 "ifaddrs.h",
+                "kvm.h",
                 "langinfo.h",
                 "libutil.h",
                 "limits.h",