Add getloadavg(3).

Lets us build ninja with bionic.

Bug: N/A
Test: ran tests
Change-Id: I97eef1247d794b58a2b9aee4851551632e5a4e48
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index 304dbb7..934ad1f 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1457,6 +1457,7 @@
     android_fdsan_get_error_level;
     android_fdsan_set_error_level;
     android_get_device_api_level;
+    getloadavg;
     pthread_sigqueue;
     reallocarray;
     timespec_get;