Rename build_system_tests to less-ambiguous test_build_system

Before it was unclear if we were building the system tests or testing
the build system.

.gitlab-ci.yml

@@ -31,7 +31,7 @@ test_build_system:
   variables:
     IDF_PATH: "$CI_PROJECT_DIR"
   script:
-    - ./make/build_system_tests.sh
+    - ./make/test_build_system.sh
 
 push_master_to_github:
   stage: deploy

make/test_build_system.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 #
-# Build system tests
+# Test the build system for basic consistency
 #
 # Just a bash script that tests some likely make failure scenarios in a row
 # Creates its own test build directory under TMP and cleans it up when done.