Do not duplicate arch properties when cpu variant == arch variant

build/make/board/generic_mips/BoardConfig.mk sets
TARGET_CPU_VARIANT := TARGET_ARCH_VARIANT, which can cause the same
variant-specific properties to be applied twice.

Test: lunch aosp_mips-eng && mmma -j external/skia TARGET_ARCH_VARIANT=mips32r2dspr2-fp
Change-Id: Ie4abe804f8ce898bf89664ae749b9bc8ac3e649f
diff --git a/android/arch.go b/android/arch.go
index a061730..df50afa 100644
--- a/android/arch.go
+++ b/android/arch.go
@@ -610,11 +610,13 @@
 		//         key: value,
 		//     },
 		// },
-		c := variantReplacer.Replace(arch.CpuVariant)
-		if c != "" {
-			field := proptools.FieldNameForProperty(c)
-			prefix := "arch." + t.Name + "." + c
-			a.appendProperties(ctx, genProps, archStruct, field, prefix)
+		if arch.CpuVariant != arch.ArchVariant {
+			c := variantReplacer.Replace(arch.CpuVariant)
+			if c != "" {
+				field := proptools.FieldNameForProperty(c)
+				prefix := "arch." + t.Name + "." + c
+				a.appendProperties(ctx, genProps, archStruct, field, prefix)
+			}
 		}
 
 		// Handle arch-feature-specific properties in the form: