[roll] Roll llvm-project/libc [libc] Support _IONBF buffering for read_unlocked (#120677)

Support _IONBF buffering for read_unlocked. Add the functions
read_unlocked_nbf() and read_unlocked_fbf().

Fixes: #120155
GitOrigin-RevId: ca3d9e698fdc1036443e70d7e393b78b7f5bb70a
Original-Revision: 9ba4b588874fffb53a78275482d2b7948f5501d7
Change-Id: If54cf185374741e9a78cc72a857b572d677ac062
diff --git a/third_party/flower b/third_party/flower
index c225b10..8978825 100644
--- a/third_party/flower
+++ b/third_party/flower
@@ -375,7 +375,7 @@
              gitsubmoduleof="fuchsia"
              path="third_party/llvm-libc/src"
              remote="https://llvm.googlesource.com/llvm-project/libc"
-             revision="93f18562252b8582af2ab8a36fcaa93cc73e6c01"/>
+             revision="9ba4b588874fffb53a78275482d2b7948f5501d7"/>
     <project name="third_party/lz4"
              gitsubmoduleof="fuchsia"
              path="third_party/lz4"