Update libc to bring in pthread mutex type definitions

diff --git a/src/liblibc b/src/liblibc
index b19b5465a1235be3323363cdc11838739b593029..45d85899e99d33e291b2bf3259881b46cc5365d7 160000 (submodule)
--- a/src/liblibc
+++ b/src/liblibc
@@ -1 +1 @@
-Subproject commit b19b5465a1235be3323363cdc11838739b593029
+Subproject commit 45d85899e99d33e291b2bf3259881b46cc5365d7