Enable code coverage for linux-auto-gcc Travis CI target.

Author: gerickson

.travis/script.sh

@@ -39,10 +39,14 @@ case "${BUILD_TARGET}" in
         ./configure && make pretty-check
         ;;
 
-    linux-auto-clang|linux-auto-gcc)
+    linux-auto-clang)
         ./configure && make && make check
         ;;
 
+    linux-auto-gcc)
+        ./configure --enable-coverage && make && make check
+        ;;
+
     osx-auto-clang)
         ./configure && make
         ;;