Allow CDM to Build With Recent GCC

(This is a merge of http://go/wvgerrit/100051. However, only one part of
that change affects the Android code, so I have filtered this
description.)

By default, the CDM builds with Clang on Android and on developers' dev
boxes. The buildbot builds most of the code with an old version of GCC.
However, recent versions of GCC were refusing to build our code for a
variety of reasons. This patch fixes the codebase up so that the
version of GCC 9 included on gLinux workstations can compile the CDM.

The only change that affects Android is that a variable was being set
but never read in one place.

Test: Android Unit Tests
Bug: 145245240
Bug: 152449437
Change-Id: Iaeb0531652bb8e7bd69f850fc6b4bba1efa3271b

libwvdrmengine/cdm/core/src/cdm_session.cpp

@@ -965,11 +965,10 @@ CdmResponseType CdmSession::RemoveKeys() {
 }
 
 CdmResponseType CdmSession::RemoveLicense() {
-  CdmResponseType sts = NO_ERROR;
   if (is_offline_ || has_provider_session_token()) {
     if (usage_support_type_ == kUsageEntrySupport &&
         has_provider_session_token()) {
-      sts = DeleteUsageEntry(usage_entry_number_);
+      DeleteUsageEntry(usage_entry_number_);
     }
     DeleteLicenseFile();
   }