folly: fix aarch64-linux build

Backports a patch that fixes memset/memcpy linking on aarch64-linux.

pkgs/by-name/fo/folly/memset-memcpy-aarch64.patch

@@ -0,0 +1,57 @@
+From 9acd1ec8e6890c7f5d86a0dd6941ae3b8692ac9c Mon Sep 17 00:00:00 2001
+From: Lukas Krenz <lkrenz@nvidia.com>
+Date: Tue, 20 Jan 2026 05:59:00 -0800
+Subject: [PATCH] Fix memset/memcpy linkage on aarch64
+
+Otherwise memcpy and memset benchmarks won't compile
+---
+ folly/CMakeLists.txt | 16 ++++++++++++++++
+ 1 file changed, 16 insertions(+)
+
+diff --git a/folly/CMakeLists.txt b/folly/CMakeLists.txt
+index a1bcbdd6e92..51280821a24 100644
+--- a/folly/CMakeLists.txt
++++ b/folly/CMakeLists.txt
+@@ -879,6 +879,9 @@ folly_add_library(
+   NAME memset-impl
+   SRCS
+     FollyMemset.cpp
++    $<$<BOOL:${IS_AARCH64_ARCH}>:memset_select_aarch64.cpp>
++  DEPS
++    $<$<BOOL:${IS_AARCH64_ARCH}>:folly_external_aor_memset_aarch64>
+ )
+ 
+ folly_add_library(
+@@ -894,12 +897,20 @@ folly_add_library(
+   EXCLUDE_FROM_MONOLITH
+   SRCS
+     FollyMemset.cpp
++    $<$<BOOL:${IS_AARCH64_ARCH}>:memset_select_aarch64.cpp>
++  DEPS
++    $<$<BOOL:${IS_AARCH64_ARCH}>:folly_external_aor_memset_aarch64-use>
++  COMPILE_OPTIONS
++    $<$<BOOL:${IS_AARCH64_ARCH}>:-DFOLLY_MEMSET_IS_MEMSET>
+ )
+ 
+ folly_add_library(
+   NAME memcpy-impl
+   SRCS
+     FollyMemcpy.cpp
++    $<$<BOOL:${IS_AARCH64_ARCH}>:memcpy_select_aarch64.cpp>
++  DEPS
++    $<$<BOOL:${IS_AARCH64_ARCH}>:folly_external_aor_memcpy_aarch64>
+ )
+ 
+ folly_add_library(
+@@ -915,6 +926,11 @@ folly_add_library(
+   EXCLUDE_FROM_MONOLITH
+   SRCS
+     FollyMemcpy.cpp
++    $<$<BOOL:${IS_AARCH64_ARCH}>:memcpy_select_aarch64.cpp>
++  DEPS
++    $<$<BOOL:${IS_AARCH64_ARCH}>:folly_external_aor_memcpy_aarch64-use>
++  COMPILE_OPTIONS
++    $<$<BOOL:${IS_AARCH64_ARCH}>:-DFOLLY_MEMCPY_IS_MEMCPY>
+ )
+ 
+ # x86 assembly memcpy implementation (not supported on MSVC)

pkgs/by-name/fo/folly/package.nix

@@ -139,6 +139,9 @@ stdenv.mkDerivation (finalAttrs: {
 
     # <https://github.com/facebook/folly/issues/2171>
     ./folly-fix-glog-0.7.patch
+
+    # https://github.com/facebook/folly/pull/2561
+    ./memset-memcpy-aarch64.patch
   ];
 
   # https://github.com/NixOS/nixpkgs/issues/144170