Add scripted for PGV protos when project has flat_package=true

For scalapb/scalapb-validate#70

src/sbt-test/integration/common-protos/build.sbt

@@ -0,0 +1,10 @@
+import scalapb.compiler.Version.protobufVersion
+
+scalaVersion := "2.13.4"
+
+Compile / PB.targets := Seq(scalapb.gen(flatPackage=true) -> (Compile / sourceManaged).value)
+
+libraryDependencies ++= Seq(
+  "com.thesamet.scalapb.common-protos" %% "pgv-proto-scalapb_0.10" % "0.4.1-1" % "protobuf",
+  "com.thesamet.scalapb.common-protos" %% "pgv-proto-scalapb_0.10" % "0.4.1-1"
+)

src/sbt-test/integration/common-protos/project/plugins.sbt

@@ -0,0 +1,11 @@
+{
+  val pluginVersion = System.getProperty("plugin.version")
+  if(pluginVersion == null)
+    throw new RuntimeException("""|The system property 'plugin.version' is not defined.
+                                  |Specify this property using the scriptedLaunchOpts -D.""".stripMargin)
+  else addSbtPlugin("com.thesamet" % "sbt-protoc" % pluginVersion)
+}
+
+libraryDependencies ++= Seq(
+  "com.thesamet.scalapb" %% "compilerplugin" % "0.10.11"
+)

src/sbt-test/integration/common-protos/src/main/protobuf/test.proto

@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+import "validate/validate.proto";
+
+message Foo {
+    validate.Int32Rules rules = 1;
+}

src/sbt-test/integration/common-protos/test

@@ -0,0 +1 @@
+> compile