[gn] fix mistake in ee99c4d

Author: nico

llvm/utils/gn/secondary/llvm/lib/Support/BUILD.gn

@@ -33,7 +33,7 @@ static_library("Support") {
     "Windows",
   ]
   sources = [
-    "AArch64BuildAttributes.cpp"
+    "AArch64BuildAttributes.cpp",
     "ABIBreak.cpp",
     "AMDGPUMetadata.cpp",
     "APFixedPoint.cpp",
@@ -42,7 +42,6 @@ static_library("Support") {
     "APSInt.cpp",
     "ARMAttributeParser.cpp",
     "ARMBuildAttrs.cpp",
-    "AArch64BuildAttributes.cpp",
     "ARMWinEH.cpp",
     "Allocator.cpp",
     "AutoConvert.cpp",