Add "//apex_available:platform" to apex_available.

When specifying apex_availabe, "//apex_available:platform" needs to be
included explicitly to allow non-apex modules to access the module.

Bug: 153022187
Bug: 152762638
Test: build
Change-Id: Ic505bb04f8ce4b12d65142ed368af9d10ff3179e
diff --git a/libs/binderthreadstate/Android.bp b/libs/binderthreadstate/Android.bp
index 9e50729..1643fda 100644
--- a/libs/binderthreadstate/Android.bp
+++ b/libs/binderthreadstate/Android.bp
@@ -21,6 +21,7 @@
     host_supported: true,
 
     apex_available: [
+        "//apex_available:platform",
         "com.android.media",
     ],
 
diff --git a/libs/gui/sysprop/Android.bp b/libs/gui/sysprop/Android.bp
index e090c49..d107ad6 100644
--- a/libs/gui/sysprop/Android.bp
+++ b/libs/gui/sysprop/Android.bp
@@ -1,6 +1,7 @@
 sysprop_library {
     name: "LibGuiProperties",
     apex_available: [
+        "//apex_available:platform",
         "com.android.media",
         "com.android.media.swcodec",
     ],