Implement sysprop type checker

sysprop type checker compares a sysprop_library API file and
property_contexts files, and detects if there are any mismatches of
property types. For example, the following snippets are detected.

// foo.sysprop
prop {
prop_name: "ro.foo.bar"
type: Integer
...
}

// property_contexts
ro.foo.bar u:object_r:foo_prop:s0 exact string

"ro.foo.bar" is an Integer in .sysprop file, but it's a string in
property_contexts file.

Bug: 151879375
Test: sysprop_test
Test: run "m PlatformProperties" and see existing mismatches.
Change-Id: Iad86d0770011e13a6d8f3e9596e730200942e3fd

sysprop/sysprop_library.go

@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"io"
 	"path"
+	"sync"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
@@ -154,8 +155,21 @@ type syspropLibraryProperties struct {
 var (
 	pctx         = android.NewPackageContext("android/soong/sysprop")
 	syspropCcTag = dependencyTag{name: "syspropCc"}
+
+	syspropLibrariesKey  = android.NewOnceKey("syspropLibraries")
+	syspropLibrariesLock sync.Mutex
 )
 
+func syspropLibraries(config android.Config) *[]string {
+	return config.Once(syspropLibrariesKey, func() interface{} {
+		return &[]string{}
+	}).(*[]string)
+}
+
+func SyspropLibraries(config android.Config) []string {
+	return append([]string{}, *syspropLibraries(config)...)
+}
+
 func init() {
 	android.RegisterModuleType("sysprop_library", syspropLibraryFactory)
 }
@@ -195,6 +209,10 @@ func (m *syspropLibrary) HasPublicStub() bool {
 	return proptools.Bool(m.properties.Public_stub)
 }
 
+func (m *syspropLibrary) CurrentSyspropApiFile() android.Path {
+	return m.currentApiFile
+}
+
 func (m *syspropLibrary) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 	baseModuleName := m.BaseModuleName()
 
@@ -463,6 +481,12 @@ func syspropLibraryHook(ctx android.LoadHookContext, m *syspropLibrary) {
 			Stem:        proptools.StringPtr(m.BaseModuleName()),
 		})
 	}
+
+	syspropLibrariesLock.Lock()
+	defer syspropLibrariesLock.Unlock()
+
+	libraries := syspropLibraries(ctx.Config())
+	*libraries = append(*libraries, ctx.ModuleName())
 }
 
 func syspropDepsMutator(ctx android.BottomUpMutatorContext) {