local build slow in opening a big file

Hello, any chance of getting an advice on an obscure kind of problem?

I've made a local build of 5.1.0.2 on my 64-bit linux box and it's showing a
peculiar behaviour when opening a 'big' file (~150 pages, bare text with
headings three levels deep).

After the (quick completing) unpacking the interface the interface goes
blank and there's a very noticeable delay before all sidebars/toolbars/*bars
and the doc show up. Over 10 seconds on my system from the start. Very annoying!

I'm comparing this with the 'stock' 5.1.0.1 build shared on the
libreoffice.org. This build shows the framework for the *bars almost
immediately after the unpacking, and the same doc comes up like in 4 seconds.

I'm not at all competent with debugger, so I could only try strace'ing the
run -- and that big time difference occurs after the swriter module is exec'ed.

So, how could I diagnose this? I rather need this local build.

At the very least, could I know the options' set with which the 'stock'
build is configured? Thanks!

For my build, I've used

./configure \
--with-external-tar=${HOME}/c/libo/ext5 \
\
--with-krb5=no \
--with-gssapi=no \
\
--disable-gstreamer-1-0 \
--disable-gstreamer-0-10 \
\
--without-fonts \
--without-junit \
--with-system-libs=no \
\
--with-system-libxml=no \
--with-system-zlib=no \