Add amd64 architecture to config.json (#1137)

use amd64 acrchitectre by default when building.
this would enable you to build the buildpack package on a arm machine

Author: ivzhelev

config.json

@@ -16,4 +16,4 @@
       }
     ]
   }
-}
+}

scripts/build.sh

@@ -29,6 +29,7 @@ function main() {
 
       CGO_ENABLED=0 \
       GOOS="${os}" \
+      GOARCH=amd64 \
         go build \
           -mod vendor \
           -ldflags="-s -w" \
@@ -38,4 +39,4 @@ function main() {
   done
 }
 
-main "${@:-}"
+main "${@:-}"