chore(ci): prohibit the build causes source changes (aws#3508)

* chore(ci): prohibit the build causes source changes

Verify that the build process does not cause changes in git tracked
files.

Fixes aws#3451

* correctly detect untracked files, too

* Update .travis.yml

* make it propper!

* add missing lockfile

.travis.yml

@@ -19,5 +19,8 @@ cache:
   - pip
 
 install: ./install.sh
-script: ./build.sh
-
+script:
+  - ./build.sh
+  - git update-index --refresh
+  - git diff-index --exit-code --stat HEAD
+  - untracked=$(git ls-files --others --exclude-standard) && echo "${untracked}" && test -z "${untracked}"

buildspec-pr.yaml

@@ -8,4 +8,4 @@ phases:
       - /bin/bash ./install.sh
   build:
     commands:
-      - /bin/bash ./build.sh
+      - /bin/bash ./build.sh && git diff-index --exit-code --ignore-space-at-eol --stat HEAD

buildspec.yaml

@@ -11,7 +11,7 @@ phases:
       - /bin/bash ./fetch-dotnet-snk.sh
   build:
     commands:
-      - /bin/bash ./build.sh
+      - /bin/bash ./build.sh && git diff-index --exit-code --ignore-space-at-eol --stat HEAD
   post_build:
     commands:
       - "[ -f .BUILD_COMPLETED ] && /bin/bash ./pack.sh"