Add soong_build primary builder

Initial build logic for building android with soong.  It can build
a variety of C and C++ files for arm/arm64 and host.

Change-Id: I10eb37c2c2a50be6af1bb5fd568c0962b9476bf0

androidmk/parser/scope.go

@@ -0,0 +1,88 @@
+package parser
+
+import "strings"
+
+type Scope interface {
+	Get(name string) string
+	Set(name, value string)
+	Call(name string, args []string) string
+	SetFunc(name string, f func([]string) string)
+}
+
+type scope struct {
+	variables map[string]string
+	functions map[string]func([]string) string
+	parent    Scope
+}
+
+func (s *scope) Get(name string) string {
+	if val, ok := s.variables[name]; ok {
+		return val
+	} else if s.parent != nil {
+		return s.parent.Get(name)
+	} else if val, ok := builtinScope[name]; ok {
+		return val
+	} else {
+		return "<'" + name + "' unset>"
+	}
+}
+
+func (s *scope) Set(name, value string) {
+	s.variables[name] = value
+}
+
+func (s *scope) Call(name string, args []string) string {
+	if f, ok := s.functions[name]; ok {
+		return f(args)
+	}
+
+	return "<func:'" + name + "' unset>"
+}
+
+func (s *scope) SetFunc(name string, f func([]string) string) {
+	s.functions[name] = f
+}
+
+func NewScope(parent Scope) Scope {
+	return &scope{
+		variables: make(map[string]string),
+		functions: make(map[string]func([]string) string),
+		parent:    parent,
+	}
+}
+
+var builtinScope map[string]string
+
+func init() {
+	builtinScope := make(map[string]string)
+	builtinScope["__builtin_dollar"] = "$"
+}
+
+func (v Variable) Value(scope Scope) string {
+	f := v.Name.SplitN(" \t", 2)
+	if len(f) > 1 && f[0].Const() {
+		fname := f[0].Value(nil)
+		if isFunctionName(fname) {
+			args := f[1].Split(",")
+			argVals := make([]string, len(args))
+			for i, a := range args {
+				argVals[i] = a.Value(scope)
+			}
+
+			if fname == "call" {
+				return scope.Call(argVals[0], argVals[1:])
+			} else {
+				return "__builtin_func:" + fname + " " + strings.Join(argVals, " ")
+			}
+		}
+	}
+
+	return scope.Get(v.Name.Value(scope))
+}
+
+func toVariable(ms *MakeString) (Variable, bool) {
+	if len(ms.Variables) == 1 && ms.Strings[0] == "" && ms.Strings[1] == "" {
+		return ms.Variables[0], true
+	}
+	return Variable{}, false
+}