filegroup.path is used to specify the include path for aidl files

filegroup {
    name: "foo",
    srcs: ["srcs/aidl/com/android/**/*.aidl"],
    path: "srcs/aidl",
}

cc_library { // or java_library, etc.
    name: "bar",
    srcs: [":foo"],
}

automatically adds "-Ipath/to/foo/srcs/aidl" when compiling the aidl
files from foo for bar. This allows us to omit aidl include path
when using sources in other places via file group.

Bug: 135922046
Test: m (unit tests added)
Change-Id: I9b42f316f2858fb6da72c2f58a314f391416e809
diff --git a/cc/gen.go b/cc/gen.go
index f8007e6..42b0cbe 100644
--- a/cc/gen.go
+++ b/cc/gen.go
@@ -120,6 +120,11 @@
 	headerBn := outDir.Join(ctx, aidlPackage, "Bn"+shortName+".h")
 	headerBp := outDir.Join(ctx, aidlPackage, "Bp"+shortName+".h")
 
+	baseDir := strings.TrimSuffix(aidlFile.String(), aidlFile.Rel())
+	if baseDir != "" {
+		aidlFlags += " -I" + baseDir
+	}
+
 	cmd := rule.Command()
 	cmd.BuiltTool(ctx, "aidl-cpp").
 		FlagWithDepFile("-d", depFile).