Make PackageVarContext implement PathGlobContext

Make PackageVarContext implement PathGlobContext by implementing
GlobWithDeps.  This will allow calls to ExistentPathForSource
inside a VariableFunc to use optimized glob dependencies instead of
falling back to AddNinjaFileDeps, which is resulting in extra
dependencies from soong_build on top level directories, triggering
extra Soong regenerations.

Remove the fallback path in ExistentPathForSource by making it take
a PathGlobContext, which is now a superset of PathContext.

Rewrite TestNinjaDeps to not rely on the unoptimized glob dependencies
in VariableFuncs and instead call ctx.Config().AddNinjaFileDeps
directly.

Bug: 257079828
Test: test_create_global_include_directory
Change-Id: I48cf189157d78b9252d339dbc9baeb27e4694807

android/package_ctx.go

@@ -48,7 +48,7 @@ type configErrorWrapper struct {
 
 var _ PathContext = &configErrorWrapper{}
 var _ errorfContext = &configErrorWrapper{}
-var _ PackageVarContext = &configErrorWrapper{}
+var _ PackageVarContext = &variableFuncContextWrapper{}
 var _ PackagePoolContext = &configErrorWrapper{}
 var _ PackageRuleContext = &configErrorWrapper{}
 
@@ -62,21 +62,33 @@ func (e *configErrorWrapper) AddNinjaFileDeps(deps ...string) {
 	e.config.addNinjaFileDeps(deps...)
 }
 
-type PackageVarContext interface {
+type variableFuncContextWrapper struct {
+	configErrorWrapper
+	blueprint.VariableFuncContext
+}
+
+type PackagePoolContext interface {
 	PathContext
 	errorfContext
 }
 
-type PackagePoolContext PackageVarContext
-type PackageRuleContext PackageVarContext
+type PackageRuleContext PackagePoolContext
+
+type PackageVarContext interface {
+	PackagePoolContext
+	PathGlobContext
+}
 
 // VariableFunc wraps blueprint.PackageContext.VariableFunc, converting the interface{} config
 // argument to a PackageVarContext.
 func (p PackageContext) VariableFunc(name string,
 	f func(PackageVarContext) string) blueprint.Variable {
 
-	return p.PackageContext.VariableFunc(name, func(config interface{}) (string, error) {
-		ctx := &configErrorWrapper{p, config.(Config), nil}
+	return p.PackageContext.VariableFunc(name, func(bpctx blueprint.VariableFuncContext, config interface{}) (string, error) {
+		ctx := &variableFuncContextWrapper{
+			configErrorWrapper:  configErrorWrapper{p, config.(Config), nil},
+			VariableFuncContext: bpctx,
+		}
 		ret := f(ctx)
 		if len(ctx.errors) > 0 {
 			return "", ctx.errors[0]