AVX2 Sigmoid accuracy evaluation stubs

PiperOrigin-RevId: 288242500
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5375c44..327748a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1081,7 +1081,13 @@
   src/math/exp-avx2-perm-p3.c
   src/math/exp-avx2-perm-p4.c
   src/math/expminus-avx2-p5.c
-  src/math/extexp-avx2-p5.c)
+  src/math/extexp-avx2-p5.c
+  src/math/sigmoid-avx2-rr2-p5-div.c
+  src/math/sigmoid-avx2-rr1-p5-div.c
+  src/math/sigmoid-avx2-rr2-p5-nr2fma.c
+  src/math/sigmoid-avx2-rr1-p5-nr2fma.c
+  src/math/sigmoid-avx2-rr2-p5-nr1fma.c
+  src/math/sigmoid-avx2-rr1-p5-nr1fma.c)
 
 SET(XNNPACK_AVX512F_MICROKERNEL_SRCS
   src/f32-clamp/avx512f.c