Update master to atlasexternals 2.0.139
Updated all projects to atlasexternals-2.0.139. The changes wrt. atlasexternals-2.0.138 are the following (atlasexternals@2.0.138...2.0.139):
- add
ATLAS_GCC_CHECKERS_CONFIG
cache variable (atlasexternals!971 (merged))
Very minor change. Does not require a full build.