exports LOCAL_SOONG_VNDK_VERSION for VNDK libs

For vndk_prebuilt_shared module, it is set by 'version' property.
For other vndk libs(e.g. cc_library with vndk.enabled), it is set as
PLATFORM_VNDK_VERSION.

Background:
To support "skip installing current VNDK".

You can get a system.img without current VNDK libs.
This may help when you want a smaller system.img given that the image
will be used with a specific version (not current) of vendor image.

Bug: 132140714
Test: m TARGET_SKIP_CURRENT_VNDK=true && see if current VNDK is not
installed

Change-Id: I1c603efc3e95fe8bdf870f2de91994077899fca7

cc/vndk.go

@@ -49,6 +49,10 @@ type VndkProperties struct {
 
 		// Extending another module
 		Extends *string
+
+		// for vndk_prebuilt_shared, this is set by "version" property.
+		// Otherwise, this is set as PLATFORM_VNDK_VERSION.
+		Version string `blueprint:"mutated"`
 	}
 }
 
@@ -325,6 +329,14 @@ func VndkMutator(mctx android.BottomUpMutatorContext) {
 		return
 	}
 
+	if m.isVndk() {
+		if lib, ok := m.linker.(*vndkPrebuiltLibraryDecorator); ok {
+			m.vndkdep.Properties.Vndk.Version = lib.version()
+		} else {
+			m.vndkdep.Properties.Vndk.Version = mctx.DeviceConfig().PlatformVndkVersion()
+		}
+	}
+
 	if _, ok := m.linker.(*llndkStubDecorator); ok {
 		processLlndkLibrary(mctx, m)
 		return