turn on doxygen build in CI (NOAA-EMC#932)

* turn on doxygen build in CI

* turn on doxygen build in CI

* turn on doxygen build in CI

* turn on doxygen build in CI

* fixed cmake file

* fixed doc directory

.github/workflows/gcc.yml

@@ -9,7 +9,7 @@ defaults:
     shell: bash -leo pipefail {0}
 
 env:
-  cache_key: gcc2  # The number (#) following the cache_key "gcc" is to flush Action cache.
+  cache_key: gcc3  # The number (#) following the cache_key "gcc" is to flush Action cache.
   CC: gcc-10
   FC: gfortran-10
   CXX: g++-10
@@ -60,6 +60,7 @@ jobs:
           sudo apt install cmake
           spack external find
           spack add [email protected]
+          spack add doxygen
           spack concretize
           spack install -v --fail-fast --dirty
           spack clean --all
@@ -91,6 +92,6 @@ jobs:
           export FC=mpif90
           cd UPP
           mkdir -p build && cd build
-          cmake -DCMAKE_INSTALL_PREFIX=../install ..
+          cmake -DENABLE_DOCS=ON -DCMAKE_INSTALL_PREFIX=../install ..
           make -j2 VERBOSE=1
           make install

CMakeLists.txt

@@ -118,7 +118,7 @@ add_subdirectory(parm)
 # If desired, build the doxygen docs.
 if(ENABLE_DOCS)
   find_package(Doxygen REQUIRED)
-  add_subdirectory(docs)
+  add_subdirectory(doc)
 endif()
 
 ### Package config

doc/Doxyfile.in

@@ -846,8 +846,8 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = @abs_top_srcdir@/docs/user_guide.md \
-                       = @abs_top_srcdir@/docs/2D-decomp.md \
+INPUT                  = @abs_top_srcdir@/doc/user_guide.md \
+                       = @abs_top_srcdir@/doc/2D-decomp.md \
                          @abs_top_srcdir@/sorc/ncep_post.fd \
                          @config_srcdir@
 
@@ -1007,7 +1007,7 @@ FILTER_SOURCE_PATTERNS =
 # (index.html). This can be useful if you have a project on for instance GitHub
 # and want to reuse the introduction page also for the doxygen output.
 
-USE_MDFILE_AS_MAINPAGE = @abs_top_srcdir@/docs/sp_user_guide.md
+USE_MDFILE_AS_MAINPAGE = @abs_top_srcdir@/doc/user_guide.md
 
 # By default, all characters from position 72 are to be considered as comment.
 # This prevents Doxygen from recognizing certain variables as undocumented