firefox-hg: fix build

gui/firefox-hg/sandbox-allow-select.patch

@@ -1,6 +1,13 @@
 --- a/security/sandbox/linux/SandboxFilter.cpp
 +++ b/security/sandbox/linux/SandboxFilter.cpp
-@@ -1999,6 +1999,9 @@
+@@ -1992,20 +1992,23 @@
+         Arg<uintptr_t> new_limit(2);
+         return If(AllOf(pid == 0, new_limit == 0), Allow())
+             .Else(InvalidSyscall());
+       }
+ #endif  // DESKTOP
+
+       // Bug 1640612
        case __NR_uname:
          return Allow();
 
@@ -10,3 +17,10 @@
        default:
          return SandboxPolicyCommon::EvaluateSyscall(sysno);
      }
+   }
+ };
+
+ UniquePtr<sandbox::bpf_dsl::Policy> GetSocketProcessSandboxPolicy(
+     SandboxBrokerClient* aMaybeBroker) {
+   return UniquePtr<sandbox::bpf_dsl::Policy>(
+       new SocketProcessSandboxPolicy(aMaybeBroker));