Fix stage for doc

.gitlab-ci.yml

@@ -13,6 +13,11 @@ build:
     expire_in: 1 day
     paths:
       - build/
+  script:
+    - cd build && cmake ..
+        -Dcpp_tools_BUILD_DOC=ON
+        -DCMAKE_C_COMPILER=gcc
+        -DCMAKE_CXX_COMPILER=g++
 
 doc:
   stage: build 
@@ -22,11 +27,7 @@ doc:
     paths:
       - build/doc/html
   script:
-    - cd build && cmake ..
-        -Dcpp_tools_BUILD_DOC=ON
-        -DCMAKE_C_COMPILER=gcc
-        -DCMAKE_CXX_COMPILER=g++
-    - make doc
+    - cd build && make doc
 
 pages:
   stage: pages