Add BR to gcc-toolset-%{gts_version}-gcc-c++

SPECS/firefox.spec

@@ -483,6 +483,7 @@ BuildRequires: gcc-toolset-%{gts_version}-runtime
 BuildRequires: gcc-toolset-%{gts_version}-binutils
 BuildRequires: gcc-toolset-%{gts_version}-gcc
 BuildRequires: gcc-toolset-%{gts_version}-gcc-plugin-annobin
+BuildRequires: gcc-toolset-%{gts_version}-gcc-c++
 # Do not explicitly require gcc-toolset-%%{gts_version}-gcc-c++ instead fail
 # when clang is upgraded to depend on a later toolset and adjust version.
 # ERROR: The target C compiler is version 13.3.1, while the target C++ compiler is version 8.5.0. Need to use the same compiler version.
@@ -2529,4 +2530,3 @@ gtk-update-icon-cache %{_datadir}/icons/hicolor &>/dev/null || :
 
 * Thu Dec  8 2016 Jan Horak <jhorak@redhat.com> - 52.0-0.5
 - Firefox Aurora 52 testing build
-