Make build-and-test-on-freebsd fail if steps to not complete successfully

This workflow is a different from most in that the entire build and test is done in a single script
in a FreeBSB QEMU constainer on an Ubuntu host. Because it is one large shell script, with no
separate "jobs", exits needed to be added to ensure the test fails if any important steps fail to
complete successfully.

Adds missing rebar3 installation required to complete the tests build.

Signed-off-by: Winford <winford@object.stream>

Author: UncleGrumpy

.github/workflows/build-and-test-on-freebsd.yaml

@@ -54,10 +54,10 @@ jobs:
         copyback: false
 
         prepare: |
-          pkg install -y curl cmake gperf erlang elixir mbedtls
+          pkg install -y curl cmake gperf erlang elixir rebar3 mbedtls
 
         run: |
-
+          set -e
           echo "%%"
           echo "%% System Info"
           echo "%%"