gcc: Use the RSB release for released tools.

Using the RSB release version for the gcc version string means the
tools have a version string that matches the release.

Close #3294

source-builder/config/gcc-common-1.cfg

@@ -38,6 +38,15 @@ BuildRoot: %{_tmppath}/%{name}-root-%(%{__id_u} -n)
  %define with_lto 0
 %endif
 
+#
+# The GCC version depends on the type of build we are doing.
+#
+%if %{rsb_released}
+ %define rtems_gcc_version %{rsb_version}
+%else
+ %define rtems_gcc_version %{rtems_version}
+%endif
+
 #
 # Prepare the source code.
 #