gitlab-ci: Only build documentation once per CMake platform

.gitlab-ci.yml

@@ -146,6 +146,7 @@ cmake:linux:gcc:shared:
   extends: .cmake:linux
   variables:
     BUILD_SHARED_LIBS: "ON"
+    CONFIG: "-DLIBXML2_WITH_DOCS=ON"
     CC: gcc
     SUFFIX: linux-gcc-shared
 
@@ -201,6 +202,7 @@ cmake:mingw:w64-i686:shared:
     - schedules
   variables:
     BUILD_SHARED_LIBS: "ON"
+    CONFIG: "-DLIBXML2_WITH_DOCS=ON"
     MSYSTEM: MINGW32
     SUFFIX: mingw-w64-i686-shared
 

.gitlab-ci/test_cmake.sh

@@ -7,11 +7,11 @@ cmake "$@" \
     -DBUILD_SHARED_LIBS=$BUILD_SHARED_LIBS \
     -DCMAKE_INSTALL_PREFIX=libxml2-install \
     -DCMAKE_BUILD_TYPE=RelWithDebInfo \
-    -DLIBXML2_WITH_DOCS=ON \
     -DLIBXML2_WITH_HTTP=ON \
     -DLIBXML2_WITH_LZMA=ON \
     -DLIBXML2_WITH_ZLIB=ON \
     -DLIBXML2_WITH_PYTHON=ON \
+    $CONFIG \
     -S . -B libxml2-build
 cmake --build libxml2-build --target install