sb/get-source: Add a macro to indicate the get-source command is running.

- Fix GDB's library checks to ignore errors when getting the source.

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

@@ -114,7 +114,7 @@
   %else
     %define gdb-python-lib-check %(%{_sbdir}/sb/rtems-build-dep -c %{__cc} %{gdb-host-libs} -l %{gdb-python-ver-lib})
   %endif
-  %if %{gdb-python-lib-check} == not-found
+  %if %{gdb-python-lib-check} == not-found && !%{_rsb_getting_source}
     %error "gdb: python: library file not found: %{gdb-python-ver-lib}, please install"
   %endif
 %endif

source-builder/sb/getsources.py

@@ -281,6 +281,7 @@ class buildset:
             self.macros = copy.copy(opts.defaults)
         else:
             self.macros = copy.copy(macros)
+        self.macros.define('_rsb_get_source')
         log.trace('_bset: %s: macro defaults' % (bset))
         log.trace(str(self.macros))
         self.bset = bset