GN: Fix gn gen/compile errors for MIPS

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index ba6b223aeec572a4377f8fe892b3e6052d418428..bfcd2ce5d7af1cead59a2a42a68a76115a1cc762 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -605,7 +605,6 @@ group("gn_only") {
       "//third_party/pdfium/third_party:freetype",
       "//third_party/libjingle:peerconnnection_server",
       "//third_party/libjpeg_turbo:simd",
-      "//third_party/libjpeg_turbo:simd_asm",
       "//third_party/libsrtp:replay_driver",
       "//third_party/libsrtp:roc_driver",
       "//third_party/libsrtp:rtpw",
@@ -632,6 +631,9 @@ group("gn_only") {
       "//ui/shell_dialogs:shell_dialogs_unittests",
       "//ui/views/examples:views_examples_exe",
     ]
+    if (target_cpu == "x86" || target_cpu == "x64") {
+      deps += [ "//third_party/libjpeg_turbo:simd_asm" ]
+    }
     if (enable_nacl) {
       deps += [ "//native_client/src/trusted/service_runtime:sel_ldr" ]
     }