fix compilation on linux
fix compilation on linux

legrosbuffle/or-tools,google/or-tools,or-tools/or-tools,google/or-tools,legrosbuffle/or-tools,or-tools/or-tools,ThatRfernand/or-tools,legrosbuffle/or-tools,google/or-tools,google/or-tools,google/or-tools,google/or-tools,legrosbuffle/or-tools,ThatRfernand/or-tools,ThatRfernand/or-tools,legrosbuffle/or-tools,or-tools/or-tools,ThatRfernand/or-tools,or-tools/or-tools,ThatRfernand/or-tools,or-tools/or-tools,or-tools/or-tools