WAsm SIMD version of PACKX microkernel

PiperOrigin-RevId: 321626936
diff --git a/BUILD.bazel b/BUILD.bazel
index c22e267..a077e46 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -788,6 +788,7 @@
     "src/f32-vunary/gen/vneg-wasmsimd-x8.c",
     "src/f32-vunary/gen/vsqr-wasmsimd-x4.c",
     "src/f32-vunary/gen/vsqr-wasmsimd-x8.c",
+    "src/x32-packx/x4-wasmsimd.c",
     "src/math/roundne-wasmsimd-addsub.c",
     "src/math/roundd-wasmsimd-addsub.c",
     "src/math/roundd-wasmsimd-cvt.c",