Run `make reset-gcov` after the script target in Travis CI is done.

This should ensure that GCDA files are never entering the cache of
Travis CI.

See: https://bugs.torproject.org/29036

.travis.yml

@@ -155,6 +155,8 @@ script:
   ## We run `make check` because that's what https://jenkins.torproject.org does.
   - if [[ "$DISTCHECK" == "" ]]; then make check; fi
   - if [[ "$DISTCHECK" != "" ]]; then make distcheck DISTCHECK_CONFIGURE_FLAGS="$CONFIGURE_FLAGS"; fi
+  ## If this build was one that produced coverage, upload it.
+  - if [[ "$COVERAGE_OPTIONS" != "" ]]; then coveralls -b . --exclude src/test --exclude src/trunnel --gcov-options '\-p'; fi
 
 after_failure:
   ## configure will leave a log file with more details of config failures.
@@ -165,9 +167,9 @@ after_failure:
   ## `make distcheck` puts it somewhere different.
   - if [[ "$DISTCHECK" != "" ]]; then make show-distdir-testlog || echo "make failed"; fi
 
-after_success:
-  ## If this build was one that produced coverage, upload it.
-  - if [[ "$COVERAGE_OPTIONS" != "" ]]; then coveralls -b . --exclude src/test --exclude src/trunnel --gcov-options '\-p'; fi
+before_cache:
+    # Delete all .gcda files.
+  - if [[ "$COVERAGE_OPTIONS" != "" ]]; then make reset-gcov; fi
 
 notifications:
   irc:

changes/bug29036

@@ -0,0 +1,5 @@
+  o Minor bugfix (continuous integration):
+    - Reset coverage state on disk after Travis CI has finished. This is being
+      done to prevent future gcda file merge errors which causes the test suite
+      for the process subsystem to fail. Fixes bug 29036; bugfix on 0.4.0.1-alpha.
+