Print environment variables in every execution (#414)

* Print environment variables in every execution

This will help us debug the failing projects on CI

Change-Id: Ibce2c1dbe51867ece0e233b575445af234a96b65

* Some refactor

Change-Id: I2e6aa8ec3d8faea65047510dd7a2e0bd4ca52a27
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 97960bf..e3154e6 100644
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -459,6 +459,8 @@
 
         print_bazel_version_info(bazel_binary)
 
+        print_environment_variables_info()
+
         if incompatible_flags:
             print_expanded_group("Build and test with the following incompatible flags:")
             for flag in incompatible_flags:
@@ -702,6 +704,12 @@
     execute_command([bazel_binary, "--nomaster_bazelrc", "--bazelrc=/dev/null", "info"])
 
 
+def print_environment_variables_info():
+    print_collapsed_group(":information_source: Environment Variables")
+    for key, value in os.environ.items():
+        eprint("%s=(%s)" % (key, value))
+
+
 def upload_bazel_binary(platform):
     print_collapsed_group(":gcloud: Uploading Bazel Under Test")
     binary_path = "bazel-bin/src/bazel"