Add option to pass custom flags to sphinx-build (#15545)

Create a SPHINX_FLAGS cache entry that users can populate with
command-line flags for sphinx-build.  Add an option to the
bootstrap script to populate it up front.

Suggested-by: Felix Geyer <debfx@ubuntu.com>

Utilities/Sphinx/CMakeLists.txt

@@ -31,8 +31,11 @@ find_program(SPHINX_EXECUTABLE
   NAMES sphinx-build
   DOC "Sphinx Documentation Builder (sphinx-doc.org)"
   )
+set(SPHINX_FLAGS "" CACHE STRING "Flags to pass to sphinx-build")
+separate_arguments(sphinx_flags UNIX_COMMAND "${SPHINX_FLAGS}")
 
 mark_as_advanced(SPHINX_TEXT)
+mark_as_advanced(SPHINX_FLAGS)
 
 if(NOT SPHINX_MAN AND NOT SPHINX_HTML AND NOT SPHINX_SINGLEHTML AND NOT SPHINX_QTHELP AND NOT SPHINX_TEXT)
   return()
@@ -114,6 +117,7 @@ foreach(format ${doc_formats})
             -c ${CMAKE_CURRENT_BINARY_DIR}
             -d ${CMAKE_CURRENT_BINARY_DIR}/doctrees
             -b ${format}
+            ${sphinx_flags}
             ${CMake_SOURCE_DIR}/Help
             ${CMAKE_CURRENT_BINARY_DIR}/${format}
             > ${doc_format_log} # log stdout, pass stderr

bootstrap

@@ -74,6 +74,7 @@ cmake_sphinx_man=""
 cmake_sphinx_html=""
 cmake_sphinx_qthelp=""
 cmake_sphinx_build=""
+cmake_sphinx_flags=""
 
 # Determine whether this is a Cygwin environment.
 if echo "${cmake_system}" | grep CYGWIN >/dev/null 2>&1; then
@@ -423,6 +424,7 @@ Configuration:
   --sphinx-html           build html help with Sphinx
   --sphinx-qthelp         build qch help with Sphinx
   --sphinx-build=<sb>     use <sb> as the sphinx-build executable
+  --sphinx-flags=<flags>  pass <flags> to sphinx-build executable
 
 Directory and file names:
   --prefix=PREFIX         install files in tree rooted at PREFIX
@@ -660,6 +662,7 @@ while test $# != 0; do
   --sphinx-html) cmake_sphinx_html="1" ;;
   --sphinx-qthelp) cmake_sphinx_qthelp="1" ;;
   --sphinx-build=*) cmake_sphinx_build=`cmake_arg "$1"` ;;
+  --sphinx-flags=*) cmake_sphinx_flags=`cmake_arg "$1"` ;;
   --help) cmake_usage ;;
   --version) cmake_version_display ; exit 2 ;;
   --verbose) cmake_verbose=TRUE ;;
@@ -1684,6 +1687,11 @@ if [ "x${cmake_sphinx_build}" != "x" ]; then
 set (SPHINX_EXECUTABLE "'"${cmake_sphinx_build}"'" CACHE FILEPATH "Location of Qt sphinx-build" FORCE)
 ' >> "${cmake_bootstrap_dir}/InitialCacheFlags.cmake"
 fi
+if [ "x${cmake_sphinx_flags}" != "x" ]; then
+  echo '
+set (SPHINX_FLAGS [==['"${cmake_sphinx_flags}"']==] CACHE STRING "Flags to pass to sphinx-build" FORCE)
+' >> "${cmake_bootstrap_dir}/InitialCacheFlags.cmake"
+fi
 
 # Add user-specified settings.  Handle relative-path case for
 # specification of cmake_init_file.