Allow customizing stripping behavior with product variable

aosp/3530072 made the default for host modules be to not strip them,
but that increases the size of our build tools prebuilts. Add a flag
that can be enabled on the build-tools build.

Test: Manually
Change-Id: I48173a52fe1a7068731ce0aca2367a0ebee0d068
diff --git a/android/config.go b/android/config.go
index 9ccd099..2a4b927 100644
--- a/android/config.go
+++ b/android/config.go
@@ -200,6 +200,11 @@
 	return c.config.productVariables.ReleaseAconfigValueSets
 }
 
+// If native modules should have symbols stripped by default. Default false, enabled for build tools
+func (c Config) StripByDefault() bool {
+	return proptools.Bool(c.config.productVariables.StripByDefault)
+}
+
 func (c Config) ReleaseAconfigExtraReleaseConfigs() []string {
 	result := []string{}
 	if val, ok := c.config.productVariables.BuildFlags["RELEASE_ACONFIG_EXTRA_RELEASE_CONFIGS"]; ok {
diff --git a/android/variable.go b/android/variable.go
index 853d8ef..9905b77 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -554,6 +554,8 @@
 	OdmManifestFiles       []string `json:",omitempty"`
 
 	UseSoongNoticeXML *bool `json:",omitempty"`
+
+	StripByDefault *bool `json:",omitempty"`
 }
 
 type PartitionQualifiedVariablesType struct {