Allow custom ar flags to be set.

Adds the ability to set custom flags for ar in Soong, similar to how
they can currently be set for make.

Bug: 36290748
Test: sanitize.go is able to correct set custom ar flags for CFI. CFI
enabled Soong components build and boot without issue.

Change-Id: I3212793aa84ba51df910c184d8bb376b3650376e

cc/builder.go

@@ -184,6 +184,7 @@ func init() {
 
 type builderFlags struct {
 	globalFlags string
+	arFlags     string
 	asFlags     string
 	cFlags      string
 	conlyFlags  string
@@ -367,6 +368,9 @@ func TransformObjToStaticLib(ctx android.ModuleContext, objFiles android.Paths,
 
 	arCmd := gccCmd(flags.toolchain, "ar")
 	arFlags := "crsPD"
+	if flags.arFlags != "" {
+		arFlags += " " + flags.arFlags
+	}
 
 	ctx.ModuleBuild(pctx, android.ModuleBuildParams{
 		Rule:      ar,

cc/cc.go

@@ -96,6 +96,7 @@ type PathDeps struct {
 
 type Flags struct {
 	GlobalFlags []string // Flags that apply to C, C++, and assembly source files
+	ArFlags     []string // Flags that apply to ar
 	AsFlags     []string // Flags that apply to assembly source files
 	CFlags      []string // Flags that apply to C and C++ source files
 	ConlyFlags  []string // Flags that apply to C source files

cc/util.go

@@ -88,6 +88,7 @@ func moduleToLibName(module string) (string, error) {
 func flagsToBuilderFlags(in Flags) builderFlags {
 	return builderFlags{
 		globalFlags: strings.Join(in.GlobalFlags, " "),
+		arFlags:     strings.Join(in.ArFlags, " "),
 		asFlags:     strings.Join(in.AsFlags, " "),
 		cFlags:      strings.Join(in.CFlags, " "),
 		conlyFlags:  strings.Join(in.ConlyFlags, " "),