Fix logic for adding gnu debuglink to match Make

Only add gnu debuglink on userdebug builds to match Make, and don't
add it when using minidebuginfo, which doesn't support it.

Bug: 113936524
Test: m checkbuild
Change-Id: Ifd529f88d63afa5627172fb6ea612aea77159f40
diff --git a/android/config.go b/android/config.go
index 3a2a005..3ef202b 100644
--- a/android/config.go
+++ b/android/config.go
@@ -572,6 +572,10 @@
 	return Bool(c.productVariables.MinimizeJavaDebugInfo) && !Bool(c.productVariables.Eng)
 }
 
+func (c *config) Debuggable() bool {
+	return Bool(c.productVariables.Debuggable)
+}
+
 func (c *config) DevicePrefer32BitExecutables() bool {
 	return Bool(c.productVariables.DevicePrefer32BitExecutables)
 }