Revert "Use the Conan package manager (XRPLF#4367)"

This reverts commit c3a9f3d.

.github/workflows/doxygen.yml

@@ -1,5 +1,4 @@
 name: Build and publish Doxygen documentation
-# To test this workflow, push your changes to your fork's `develop` branch.
 on:
   push:
     branches:
@@ -12,18 +11,12 @@ jobs:
       image: docker://rippleci/rippled-ci-builder:2944b78d22db
     steps:
       - name: checkout
-        uses: actions/checkout@v3
-      - name: check environment
-        run: |
-          echo ${PATH} | tr ':' '\n'
-          cmake --version
-          doxygen --version
-          env
+        uses: actions/checkout@v2
       - name: build
         run: |
           mkdir build
           cd build
-          cmake -Donly_docs=TRUE ..
+          cmake -DBoost_NO_BOOST_CMAKE=ON ..
           cmake --build . --target docs --parallel $(nproc)
       - name: publish
         uses: peaceiris/actions-gh-pages@v3

.gitignore

@@ -26,6 +26,7 @@ build/docker
 
 # Ignore object files.
 *.o
+build
 .nih_c
 tags
 TAGS
@@ -69,7 +70,7 @@ docs/html_doc
 # Xcode user-specific project settings
 # Xcode
 .DS_Store
-/build/
+*/build/*
 *.pbxuser
 !default.pbxuser
 *.mode1v3