[roll] Roll cobalt [clang] Add missing headers after libc++ update

In llvm/llvm-project#99738 libc++ removed cmath
from one of its header files, and several places in Fuchsia are no
longer including the required header for rounding functions.

Original-Bug: 359865937
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/cobalt/+/1100813
Original-Revision: 80f803c32ad67dc22d9cb84273f16a736fe2db7b
GitOrigin-RevId: e9d3d70a0c7c65a201e9087f9f526d30db1cb3bc
Change-Id: Id85d25288760dfb087fcbd460e7b222c927b0cda

Author: Paul Kirth

third_party/flower

@@ -98,7 +98,7 @@
              gitsubmoduleof="fuchsia"
              path="third_party/cobalt"
              remote="https://fuchsia.googlesource.com/cobalt"
-             revision="d73cd43ab9254aaaaf22e974098282f1150db28c"
+             revision="80f803c32ad67dc22d9cb84273f16a736fe2db7b"
              gerrithost="https://fuchsia-review.googlesource.com"/>
     <project name="cobalt-registry"
              gitsubmoduleof="fuchsia"