curl-autotools.sh: must enable docs for curl manual [ci skip]

Ref: curl/curl#13191

Author: vszakats

curl-autotools.sh

@@ -411,12 +411,12 @@ _VER="$1"
 
   if [[ "${_CONFIG}" = *'nocurltool'* ]]; then
     options+=' --disable-manual'
+    options+=' --disable-docs'  # Skip building documentation in man page format
   else
     options+=' --enable-manual'
+    options+=' --enable-docs'  # Required for `--enable-manual`
   fi
 
-  options+=' --disable-docs'  # Skip building documentation in man page format
-
   options+=' --enable-static --enable-shared'
 
   (