Add buildDir to java patch-module paths.

This solves a problem where javac fails to find patch-module targets
when a build diretory is not under the project root.

Bug: 117770838
Test: java_test.go + manual build
Change-Id: If70d0d388a3f6c87b3f78a927df2063616d50c8a

android/module.go

@@ -190,6 +190,7 @@ type Module interface {
 	GetProperties() []interface{}
 
 	BuildParamsForTests() []BuildParams
+	VariablesForTests() map[string]string
 }
 
 type nameProperties struct {
@@ -473,6 +474,7 @@ type ModuleBase struct {
 
 	// For tests
 	buildParams []BuildParams
+	variables   map[string]string
 
 	prefer32 func(ctx BaseModuleContext, base *ModuleBase, class OsClass) bool
 }
@@ -489,6 +491,10 @@ func (a *ModuleBase) BuildParamsForTests() []BuildParams {
 	return a.buildParams
 }
 
+func (a *ModuleBase) VariablesForTests() map[string]string {
+	return a.variables
+}
+
 func (a *ModuleBase) Prefer32(prefer32 func(ctx BaseModuleContext, base *ModuleBase, class OsClass) bool) {
 	a.prefer32 = prefer32
 }
@@ -781,6 +787,7 @@ func (a *ModuleBase) GenerateBuildActions(blueprintCtx blueprint.ModuleContext)
 		installDeps:            a.computeInstallDeps(blueprintCtx),
 		installFiles:           a.installFiles,
 		missingDeps:            blueprintCtx.GetMissingDependencies(),
+		variables:              make(map[string]string),
 	}
 
 	desc := "//" + ctx.ModuleDir() + ":" + ctx.ModuleName() + " "
@@ -842,6 +849,7 @@ func (a *ModuleBase) GenerateBuildActions(blueprintCtx blueprint.ModuleContext)
 	}
 
 	a.buildParams = ctx.buildParams
+	a.variables = ctx.variables
 }
 
 type androidBaseContextImpl struct {
@@ -864,6 +872,7 @@ type androidModuleContext struct {
 
 	// For tests
 	buildParams []BuildParams
+	variables   map[string]string
 }
 
 func (a *androidModuleContext) ninjaError(desc string, outputs []string, err error) {
@@ -928,6 +937,10 @@ func convertBuildParams(params BuildParams) blueprint.BuildParams {
 }
 
 func (a *androidModuleContext) Variable(pctx PackageContext, name, value string) {
+	if a.config.captureBuild {
+		a.variables[name] = value
+	}
+
 	a.ModuleContext.Variable(pctx.PackageContext, name, value)
 }