style(ci): add commands for removing test-reports

Bitbucket Pipelines has some weird default behavior on how artifacts are
archived and JUnit test-reports are parsed on every subsequent run, if the
output was once an artifact. It's confusing to look at via the dashboard, hence
I'm adding an override to remove them beforehand.

bitbucket-pipelines.yml

@@ -26,6 +26,7 @@ definitions:
                 - build/debug/**/*
                 - build/debug/*
             script:
+                - make clean
                 - make build/debug CI=1
         - step: &build-release
             name: Build (Release)
@@ -35,6 +36,7 @@ definitions:
                 - build/release/**/*
                 - build/release/*
             script:
+                - make clean
                 - make build/release CI=1
         - step: &build-doc
             name: Build (Doc)
@@ -44,6 +46,7 @@ definitions:
                 - build/doc/**/*
                 - build/doc/*
             script:
+                - make clean
                 - make build/doc CI=1
         - step: &dist
             name: Package
@@ -52,6 +55,7 @@ definitions:
             artifacts:
                 - dist/*
             script:
+                - rm -rvf test-reports/
                 - make dist CI=1
 pipelines:
     default: