Avoid re-downloading and rebuilding gogo every time we run codegen

This is a quality of life change to make running `rake codegen` locally faster

.gitignore

@@ -11,4 +11,8 @@
 # jetbrains IDE directory
 /.idea/
 
-vendor/
+vendor/
+
+# build time dependencies that are either downloaded or
+# built during codegen
+toolchains/

Rakefile

@@ -4,14 +4,33 @@
 
 protoc_binary="protoc"
 protoc_version="3.5.1"
-gogo_dir="/tmp/gogo"
+gogo_dir=Dir.pwd + "/toolchains/gogo"
+gogo_bin=Dir.pwd + "/toolchains/gogo-bin-v1.3.2"
 protoc_binary_2="protoc"
 protoc_version_2="21.12"
 protoc_gen_go_dir="/tmp/protoc-gen-go"
 protoc_jsonschema_version="73d5723"
 
 
 namespace :codegen do
+  task :clean do
+      sh "rm -rf #{gogo_dir}"
+  end
+
+  task :setup_gogo do
+    if ! Dir.exist?(gogo_dir) then
+      sh "mkdir -p #{gogo_dir}/src/github.com/gogo"
+      sh "git clone https://github.com/gogo/protobuf.git #{gogo_dir}/src/github.com/gogo/protobuf"
+    else
+      puts "gogo already cloned into #{gogo_dir}"
+    end
+    sh <<-EOD
+      # Install v1.3.2
+      pushd #{gogo_dir}/src/github.com/gogo/protobuf
+      git checkout v1.3.2
+      GOBIN=#{gogo_bin} GOPATH=#{gogo_dir} make clean install
+EOD
+  end
 
   task :install_protoc do
     if `bash -c "protoc --version"` != "libprotoc ${protoc_version}"
@@ -52,37 +71,24 @@ BASH
     end
   end
 
-  task :protoc => ['install_protoc'] do
+  task :protoc => ['install_protoc', 'setup_gogo'] do
     sh <<-EOF
       /bin/bash <<BASH
       set -euo pipefail
 
       export GO111MODULE=auto
 
-      rm -rf #{gogo_dir}
-      rm -rf /tmp/gogo-bin-*
-
-      mkdir -p #{gogo_dir}/src/github.com/gogo
-      git clone https://github.com/gogo/protobuf.git #{gogo_dir}/src/github.com/gogo/protobuf
-
-      # Install v1.3.2
-      pushd #{gogo_dir}/src/github.com/gogo/protobuf
-      git checkout v1.3.2
-      GOBIN=/tmp/gogo-bin-v1.3.2 GOPATH=#{gogo_dir} make clean install
-
-      popd
-
       echo "Generating logs proto"
-      PATH=/tmp/gogo-bin-v1.3.2 #{protoc_binary} --proto_path=$GOPATH/src:#{gogo_dir}/src:. --gogofast_out=$GOPATH/src --java_out=java proto/logs/agent_logs_payload.proto
+      PATH=#{gogo_bin}  #{protoc_binary} --proto_path=$GOPATH/src:#{gogo_dir}/src:. --gogofast_out=$GOPATH/src --java_out=java proto/logs/agent_logs_payload.proto
 
       echo "Generating metrics proto (go)"
-      PATH=/tmp/gogo-bin-v1.3.2 #{protoc_binary} --proto_path=$GOPATH/src:#{gogo_dir}/src:. --gogofast_out=$GOPATH/src proto/metrics/agent_payload.proto
+      PATH=#{gogo_bin} #{protoc_binary} --proto_path=$GOPATH/src:#{gogo_dir}/src:. --gogofast_out=$GOPATH/src proto/metrics/agent_payload.proto
 
       echo "Generating metrics proto (python)"
       #{protoc_binary} --proto_path=#{gogo_dir}/src:$GOPATH/src:./proto/metrics --python_out=python agent_payload.proto
 
       echo "Generating process proto (go)"
-      PATH=/tmp/gogo-bin-v1.3.2 #{protoc_binary} --proto_path=$GOPATH/src:#{gogo_dir}/src:. --gogofaster_out=$GOPATH/src proto/process/*.proto
+      PATH=#{gogo_bin} #{protoc_binary} --proto_path=$GOPATH/src:#{gogo_dir}/src:. --gogofaster_out=$GOPATH/src proto/process/*.proto
 
       GOPATH=#{protoc_gen_go_dir} go install github.com/leeavital/protoc-gen-gostreamer@v0.1.0
       PATH=#{protoc_gen_go_dir}/bin #{protoc_binary} --proto_path=$GOPATH/src:#{gogo_dir}/src:.  --gostreamer_out=$GOPATH/src proto/process/*.proto