build: Fix compilation in 32 bits platforms (#4052)
build: Fix compilation in 32 bits platforms (#4052)

go fails to build Minio under at least, armv6 and 386 due to some
inconsistencies in the type of one syscall variable in different
architectures. This PR casts that variable to uint64 to achieve
the desired consistency.
aead/minio,hackintoshrao/minio,harshavardhana/minio,fwessels/minio,NitishT/minio,aead/minio,brendanashworth/minio,krishnasrinivas/minio,brendanashworth/minio,aead/minio,NitishT/minio,dutchcoders/minio,krisis/minio,luomeiqin/minio,rushenn/minio,hackintoshrao/minio,rushenn/minio,aead/minio,harshavardhana/minio,donatello/minio,brendanashworth/minio,hackintoshrao/minio,fwessels/minio,aead/minio,abperiasamy/minio,dutchcoders/minio,hackintoshrao/minio,dvstate/minio,minio/minio,dvstate/minio,abperiasamy/minio,rushenn/minio,harshavardhana/minio,aead/minio,vadmeste/minio,rushenn/minio,luomeiqin/minio,harshavardhana/minio,jimjag/minio,luomeiqin/minio,abperiasamy/minio,dutchcoders/minio,jimjag/minio,NitishT/minio,minio/minio,balamurugana/minio,jimjag/minio,krisis/minio,fwessels/minio,dvstate/minio,krishnasrinivas/minio,vadmeste/minio,harshavardhana/minio,dutchcoders/minio,donatello/minio,harshavardhana/minio,balamurugana/minio,aead/minio,abperiasamy/minio,luomeiqin/minio,harshavardhana/minio,harshavardhana/minio,dvstate/minio,NitishT/minio,brendanashworth/minio,jimjag/minio,krishnasrinivas/minio,fwessels/minio,aead/minio,krishnasrinivas/minio