configure: move --enable-docs and --disable-docs back to configure

Move this option back from meson into configure for the purposes of
using the configuration value to bootstrap Sphinx in different ways
based on this value.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20230511035435.734312-21-jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -279,6 +279,7 @@ debug_tcg="no"
 sanitizers="no"
 tsan="no"
 fortify_source="yes"
+docs="auto"
 EXESUF=""
 modules="no"
 prefix="/usr/local"
@@ -750,6 +751,10 @@ for opt do
   ;;
   --disable-debug-info) meson_option_add -Ddebug=false
   ;;
+  --enable-docs) docs=enabled
+  ;;
+  --disable-docs) docs=disabled
+  ;;
   --enable-modules)
       modules="yes"
   ;;
@@ -2615,6 +2620,7 @@ if test "$skip_meson" = no; then
 
   # QEMU options
   test "$cfi" != false && meson_option_add "-Dcfi=$cfi"
+  test "$docs" != auto && meson_option_add "-Ddocs=$docs"
   test "$fdt" != auto && meson_option_add "-Dfdt=$fdt"
   test -n "${LIB_FUZZING_ENGINE+xxx}" && meson_option_add "-Dfuzzing_engine=$LIB_FUZZING_ENGINE"
   test "$qemu_suffix" != qemu && meson_option_add "-Dqemu_suffix=$qemu_suffix"