component/defaults: Allow to force gcc from SlapOS

In some environments it is required to have gcc provided by SlapOS, and simply
forcing seems better than setting bugs min_version.

component/defaults.cfg

@@ -38,6 +38,8 @@ part = gcc-8.2
 # Minimum version for all components that might be required for
 # slapos.rebootstrap (see https://bugs.python.org/issue34112 about Python 3.7+).
 min_version = 5.4
+# A switch for environments which want to force slapos provided gcc
+force_slapos_gcc = False
 init =
   import os, subprocess
   parse_version = lambda ver: tuple(map(int, ver.strip().split('.')))
@@ -53,8 +55,9 @@ init =
   # the conditions have no impact on the dependant parts.
   min_version = options.pop('min_version', None)
   max_version = options.pop('max_version', None)
+  force_slapos_gcc = options.pop('force_slapos_gcc', 'False').lower() == 'true'
   ###
-  if (parse_version(min_version or current)
+  if (not force_slapos_gcc) and (parse_version(min_version or current)
       <= parse_version(current)
       <= parse_version(max_version or current)):
     del options['part']