Soong: Add synopsis to several modules under cc package.

Added synopsis to the following modules under cc package:
    * cc_binary
    * cc_binary_host
    * cc_defaults
    * cc_genrule
    * cc_test
    * cc_test_host

Bug: b/128337482
Test: Generated the documentation and verified that the
synopsis was added to each of the module.

Change-Id: I23b7eda449c340783d7cc592df5d2bd399255bf9
diff --git a/cc/binary.go b/cc/binary.go
index 7f7c600..60ef2ce 100644
--- a/cc/binary.go
+++ b/cc/binary.go
@@ -57,13 +57,13 @@
 	android.RegisterModuleType("cc_binary_host", binaryHostFactory)
 }
 
-// Module factory for binaries
+// cc_binary produces a binary that is runnable on a device.
 func BinaryFactory() android.Module {
 	module, _ := NewBinary(android.HostAndDeviceSupported)
 	return module.Init()
 }
 
-// Module factory for host binaries
+// cc_binary_host produces a binary that is runnable on a host.
 func binaryHostFactory() android.Module {
 	module, _ := NewBinary(android.HostSupported)
 	return module.Init()