Fix llvm-ar error caused by using lto and sanitizer together

LLVM-AR does not allow passing --plugin options more than once. The
--plugin ARFLAGS that lto want to add, may already exist if sanitizer is
also turned on.

Fixed this by adding a new bool Flags.ArGoldPlugin. Set this variable to
true whenever LLVM gold plugin is needed for ArFlags. In function
TransformObjToStaticLib(), add this option to arFlags using global value
${config.LLVMGoldPlugin} if the bool value is true.

Bug: http://b/73160350
Test: build the image with make and succeeded.

Change-Id: I62785829b0a4b663225926e4aed98defc1b6da2c
(cherry picked from commit 4917049f6efe2d08e67eb26ec77e21dcce5172c5)
diff --git a/cc/sanitize.go b/cc/sanitize.go
index ac6cb77..c47c319 100644
--- a/cc/sanitize.go
+++ b/cc/sanitize.go
@@ -38,7 +38,6 @@
 		"-fsanitize-blacklist=external/compiler-rt/lib/cfi/cfi_blacklist.txt"}
 	cfiLdflags = []string{"-flto", "-fsanitize-cfi-cross-dso", "-fsanitize=cfi",
 		"-Wl,-plugin-opt,O1"}
-	cfiArflags         = []string{"--plugin ${config.ClangBin}/../lib64/LLVMgold.so"}
 	cfiExportsMapPath  = "build/soong/cc/config/cfi_exports.map"
 	cfiExportsMap      android.Path
 	cfiStaticLibsMutex sync.Mutex
@@ -407,7 +406,7 @@
 			// See b/72706604 or https://github.com/android-ndk/ndk/issues/498.
 			flags.LdFlags = append(flags.LdFlags, "-Wl,-plugin-opt,-emulated-tls")
 		}
-		flags.ArFlags = append(flags.ArFlags, cfiArflags...)
+		flags.ArGoldPlugin = true
 		if Bool(sanitize.Properties.Sanitize.Diag.Cfi) {
 			diagSanitizers = append(diagSanitizers, "cfi")
 		}