cc Bp2build support for genrules that generate .proto file

If `srcs` contains a gensrcs/genrule module, the current bp2build module
will put it in the catch-all `srcs` attribute. This is reserved for .cpp
sources, so if the genrule produces a .proto/.aidl/... file, this will
fail.

This handles genrules that produce .proto files. To implement this, this
creates an additional partition that detects if the other module is a
genrule/gensrc that produces .proto files. If true, it will append it to
the proto partition.

This CL does not handle
- genrule that produce .c/.aidl/.yacc/.... files. They will continue to
  be partitioned into the catch-all partition
- java modules

Test: unit tests
Test: TH
Bug: 293205700
Change-Id: Ib720fdf3a053ff5dd256e6faa632e3fa7776966d

genrule/genrule.go

@@ -1012,16 +1012,7 @@ func (m *Module) ConvertWithBp2build(ctx android.TopDownMutatorContext) {
 			Tags: tags,
 		}, attrs)
 	} else {
-		// The Out prop is not in an immediately accessible field
-		// in the Module struct, so use GetProperties and cast it
-		// to the known struct prop.
-		var outs []string
-		for _, propIntf := range m.GetProperties() {
-			if props, ok := propIntf.(*genRuleProperties); ok {
-				outs = props.Out
-				break
-			}
-		}
+		outs := m.RawOutputFiles(ctx)
 		for _, out := range outs {
 			if out == bazelName {
 				// This is a workaround to circumvent a Bazel warning where a genrule's
@@ -1096,6 +1087,25 @@ type ccHeaderLibraryAttrs struct {
 	Export_includes []string
 }
 
+// RawOutputFfiles returns the raw outputs specified in Android.bp
+// This does not contain the fully resolved path relative to the top of the tree
+func (g *Module) RawOutputFiles(ctx android.BazelConversionContext) []string {
+	if ctx.Config().BuildMode != android.Bp2build {
+		ctx.ModuleErrorf("RawOutputFiles is only supported in bp2build mode")
+	}
+	// The Out prop is not in an immediately accessible field
+	// in the Module struct, so use GetProperties and cast it
+	// to the known struct prop.
+	var outs []string
+	for _, propIntf := range g.GetProperties() {
+		if props, ok := propIntf.(*genRuleProperties); ok {
+			outs = props.Out
+			break
+		}
+	}
+	return outs
+}
+
 var Bool = proptools.Bool
 var String = proptools.String