[roll] Roll fuchsia [libc] Remove some __* symbols from the abi.

It seems likely that these symbols should have been hidden and
were used at one point as a way for libc to use the internal
symbol without fear of using the potentially interposed public
one. These symbols are not referenced from within libc, or in the
rest of Fuchsia's tree. Though we will do an lsc + wait the requisite
time before pushing.

I'm not sure if strdup should be weak or not. It is in glibc, but
it seems they are very liberal with making things weak. Note, the
distinction here will matter if fxrev.dev/772922 lands.

This will be useful when transitioning to llvm-libc string functions
because their implementation does not export these symbols.

Original-Bug: 62780
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/788102
Original-Revision: a6f912245757f9fe59e8341ce1ea4551a958f822
GitOrigin-RevId: 4f119d56ed6eba8e1dc5bc33b1d64387814424a2
Change-Id: Id436f631ba78ac008af3a654e2d4153e42c81ff4
diff --git a/stem b/stem
index 633d110..ff51023 100644
--- a/stem
+++ b/stem
@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="6816aaecb5cd949fc9a8c08b850a9f2af4574e7b"/>
+             revision="a6f912245757f9fe59e8341ce1ea4551a958f822"/>
   </projects>
   <hooks>
     <hook name="install-environment"