Merge pull request #90 from ava-labs/feuGeneA-patch-2

README additions for build & test instructions

README.md

@@ -6,6 +6,8 @@ Reference relayer implementation for cross-chain Avalanche Warp Message delivery
 
 ### Building
 
+Before building, be sure to install Go, which is required even if you're just building the Docker image.
+
 Build the relayer by running the script:
 
 ```bash
@@ -140,6 +142,8 @@ Unit tests can be ran locally by running the command in the root of the project:
 ./scripts/test.sh
 ```
 
+If your temporary directory is not writable, the unit tests may fail with messages like `fork/exec /tmp/go-build2296620589/b247/config.test: permission denied`. To fix this, set the `TMPDIR` environment variable to something writable, eg `export TMPDIR=~/tmp`.
+
 ### E2E tests
 
 E2E tests are ran as part of CI, but can also be ran locally with the `--local` flag. To run the E2E tests locally, you'll need to install Gingko following the intructions [here](https://onsi.github.io/ginkgo/#installing-ginkgo)