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

cc/binary.go

@@ -57,13 +57,13 @@ func init() {
 	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()

cc/cc.go

@@ -1966,6 +1966,11 @@ type Defaults struct {
 func (*Defaults) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 }
 
+// cc_defaults provides a set of properties that can be inherited by other cc
+// modules. A module can use the properties from a cc_defaults using
+// `defaults: ["<:default_module_name>"]`. Properties of both modules are
+// merged (when possible) by prepending the default module's values to the
+// depending module's values.
 func defaultsFactory() android.Module {
 	return DefaultsFactory()
 }

cc/test.go

@@ -74,31 +74,41 @@ func init() {
 	android.RegisterModuleType("cc_benchmark_host", BenchmarkHostFactory)
 }
 
-// Module factory for tests
+// cc_test generates a test config file and an executable binary file to test
+// specific functionality on a device. The executable binary gets an implicit
+// static_libs dependency on libgtests unless the gtest flag is set to false.
 func TestFactory() android.Module {
 	module := NewTest(android.HostAndDeviceSupported)
 	return module.Init()
 }
 
-// Module factory for test libraries
+// cc_test_library creates an archive of files (i.e. .o files) which is later
+// referenced by another module (such as cc_test, cc_defaults or cc_test_library)
+// for archiving or linking.
 func TestLibraryFactory() android.Module {
 	module := NewTestLibrary(android.HostAndDeviceSupported)
 	return module.Init()
 }
 
-// Module factory for benchmarks
+// cc_benchmark compiles an executable binary that performs benchmark testing
+// of a specific component in a device. Additional files such as test suites
+// and test configuration are installed on the side of the compiled executed
+// binary.
 func BenchmarkFactory() android.Module {
 	module := NewBenchmark(android.HostAndDeviceSupported)
 	return module.Init()
 }
 
-// Module factory for host tests
+// cc_test_host compiles a test host binary.
 func TestHostFactory() android.Module {
 	module := NewTest(android.HostSupported)
 	return module.Init()
 }
 
-// Module factory for host benchmarks
+// cc_benchmark_host compiles an executable binary that performs benchmark
+// testing of a specific component in the host. Additional files such as
+// test suites and test configuration are installed on the side of the
+// compiled executed binary.
 func BenchmarkHostFactory() android.Module {
 	module := NewBenchmark(android.HostSupported)
 	return module.Init()