Soong: Add synopsis to cc_object module.

Added synopsis to the cc_object module.

Bug: b/128337482
Test: Generated the documentation and verified that the synopsis was
properly added.

Change-Id: Icba4522a3aafa1b8b8a0b780d111f8b48cbdd270

cc/object.go

@@ -33,6 +33,9 @@ type objectLinker struct {
 	Properties ObjectLinkerProperties
 }
 
+// cc_object runs the compiler without running the linker. It is rarely
+// necessary, but sometimes used to generate .s files from .c files to use as
+// input to a cc_genrule module.
 func ObjectFactory() android.Module {
 	module := newBaseModule(android.HostAndDeviceSupported, android.MultilibBoth)
 	module.linker = &objectLinker{