Create a new product variable to gate blueprint files

Users can use this feature by
1. Setting PRODUCT_INCLUDE_TAGS += <val> in their product mk files
2. Set
```
blueprint_packge_includes {
  match_al: ["<val>"],
}

other_module_type {name: foo}
other_module_type {name: bar}
```

bar and foo will be included if and only if <val> is set

Test: Unit tests in blueprint
Test: TH

Change-Id: I32eed4e3b5ac47fb565c62d13d8881fa984c86f4
diff --git a/ui/build/config.go b/ui/build/config.go
index 7651a0f..ef2e87e 100644
--- a/ui/build/config.go
+++ b/ui/build/config.go
@@ -111,6 +111,8 @@
 	metricsUploader string
 
 	bazelForceEnabledModules string
+
+	includeTags []string
 }
 
 const srcDirFileCheck = "build/soong/root.bp"
@@ -1079,6 +1081,14 @@
 	return c.parallel
 }
 
+func (c *configImpl) GetIncludeTags() []string {
+	return c.includeTags
+}
+
+func (c *configImpl) SetIncludeTags(i []string) {
+	c.includeTags = i
+}
+
 func (c *configImpl) HighmemParallel() int {
 	if i, ok := c.environ.GetInt("NINJA_HIGHMEM_NUM_JOBS"); ok {
 		return i