Add gensrcs module type

gensrcs allows sources to be generated by a specified command.

Change-Id: I725086fcdcd72bfe6c07fb8903e7b520678a247f

cmd/soong_build/main.go

@@ -26,6 +26,7 @@ import (
 	"android/soong/cc"
 	"android/soong/common"
 	"android/soong/config"
+	"android/soong/genrule"
 )
 
 func main() {
@@ -50,6 +51,8 @@ func main() {
 	ctx.RegisterModuleType("cc_library_host_shared", cc.NewCCLibraryHostShared)
 	ctx.RegisterModuleType("cc_binary_host", cc.NewCCBinaryHost)
 
+	ctx.RegisterModuleType("gensrcs", genrule.NewGenSrcs)
+
 	// Mutators
 	ctx.RegisterEarlyMutator("arch", common.ArchMutator)
 	ctx.RegisterEarlyMutator("link", cc.LinkageMutator)