Convert abi warnings to errors.

Convert abi warnings to errors by removing the -advice-only flag from
the invocation of header-abi-diff. This will only apply to branches with
reference abi dumps checked into prebuilts/abi-dumps/(v)ndk (since
abi-diffing will only be triggered on them.)

Also allow for:

1) Extensions.
2) Changes to types in exported headers, unreferenced by public symbols still
   trigger warnings.
3) Any removal of symbols appearing in a shared library's .dynsym table, but not
   in exported headers is still a warning.

Bug: 64267858

Test: make -j64 from ToT.

Change-Id: Iadeac8d060cb693d4310afb841dc48d91f38597d

cc/builder.go

@@ -36,6 +36,14 @@ const (
 	staticLibraryExtension = ".a"
 )
 
+var (
+	abiCheckAllowFlags = []string{
+		"-allow-extensions",
+		"-allow-unreferenced-changes",
+		"-allow-unreferenced-elf-symbol-changes",
+	}
+)
+
 var (
 	pctx = android.NewPackageContext("android/soong/cc")
 
@@ -191,10 +199,10 @@ var (
 	// Abidiff check turned on in advice-only mode. Builds will not fail on abi incompatibilties / extensions.
 	sAbiDiff = pctx.AndroidStaticRule("sAbiDiff",
 		blueprint.RuleParams{
-			Command:     "$sAbiDiffer -lib $libName -arch $arch -advice-only -check-all-apis -o ${out} -new $in -old $referenceDump",
+			Command:     "$sAbiDiffer $allowFlags -lib $libName -arch $arch -check-all-apis -o ${out} -new $in -old $referenceDump",
 			CommandDeps: []string{"$sAbiDiffer"},
 		},
-		"referenceDump", "libName", "arch")
+		"allowFlags", "referenceDump", "libName", "arch")
 
 	unzipRefSAbiDump = pctx.AndroidStaticRule("unzipRefSAbiDump",
 		blueprint.RuleParams{
@@ -709,6 +717,7 @@ func SourceAbiDiff(ctx android.ModuleContext, inputDump android.Path, referenceD
 			"referenceDump": referenceDump.String(),
 			"libName":       baseName,
 			"arch":          ctx.Arch().ArchType.Name,
+			"allowFlags":    strings.Join(abiCheckAllowFlags, " "),
 		},
 	})
 	return android.OptionalPathForPath(outputFile)