Only enable race detector when GOHOSTARCH is amd64.
Only enable race detector when GOHOSTARCH is amd64.

This enables native builds to still run the test and all targets without
problems on say 386.

Build failure on Buildkite build 85, prevents enabling native FreeBSD
386 builds.

derekmarcotte/node_exporter,Jean-Daniel/node_exporter,derekmarcotte/node_exporter,siavashs/node_exporter,prometheus/node_exporter,Jean-Daniel/node_exporter,derekmarcotte/node_exporter,siavashs/node_exporter,prometheus/node_exporter,joehandzik/node_exporter,joehandzik/node_exporter,joehandzik/node_exporter,derekmarcotte/node_exporter,siavashs/node_exporter,Jean-Daniel/node_exporter,Jean-Daniel/node_exporter,joehandzik/node_exporter,siavashs/node_exporter,prometheus/node_exporter