Fix unused-command-line-argument warning

Limit -msse2 flag to x86/x86_64 targets only.

Test: build
Bug: 197177755
Change-Id: I013deec2e0737477b4594d1204ac6d6e0348cde3
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/57648
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Yi Kong <yikong@google.com>
Commit-Queue: Yi Kong <yikong@google.com>
diff --git a/Android.bp b/Android.bp
index b40af64..6931936 100644
--- a/Android.bp
+++ b/Android.bp
@@ -57,7 +57,6 @@
     gnu_extensions: false,
 
     cflags: [
-        "-msse2",
         "-Werror",
         "-Wwrite-strings",
     ],
@@ -69,6 +68,19 @@
     ],
     cpp_std: "c++17",
 
+    arch: {
+        x86: {
+            cflags: [
+                "-msse2",
+            ],
+        },
+        x86_64: {
+            cflags: [
+                "-msse2",
+            ],
+        },
+    },
+
     target: {
         host: {
             cppflags: [