Do not check for GOPATH env for builds (#5628)

Since go1.8 GOPATH is not required to set prior, as
it defaults to "${HOME}/go" we only need to check if
go tool detected GOPATH correctly. If yes then we
proceed if not we fail.

buildscripts/checkdeps.sh

@@ -128,12 +128,6 @@ assert_check_golang_env() {
         echo "Go runtime version '${installed_go_version}' is unsupported. Minimum supported version: ${GO_VERSION} to compile."
         exit 1
     fi
-
-    if [ -z "${GOPATH}" ]; then
-        echo "GOPATH environment variable missing, please refer to Go installation document at https://docs.minio.io/docs/how-to-install-golang"
-        exit 1
-    fi
-
 }
 
 assert_check_deps() {