While building wv 1.0.0, libtool is invoked as such:

/bin/sh ./libtool --mode=link gcc  -pipe -Wall -O3 -march=i686 -ansi   -o
libwv.la -rpath /usr/lib -version-info 0:0:0 -release 1.0 -export-dynamic
winmmap.lo support.lo list.lo stylesheet.lo sprm.lo blip.lo utf.lo field.lo
decompresswmf.lo dop.lo roman.lo fib.lo frd.lo atrd.lo sed.lo font.lo ffn.lo
fld.lo bkf.lo dttm.lo generic.lo error.lo unicode.lo sttbf.lo xst.lo fspa.lo
fdoa.lo lst.lo lvl.lo
lfo.lo filetime.lo chp.lo brc.lo anld.lo shd.lo dcs.lo numrm.lo asumyi.lo
version.lo lspd.lo phe.lo tlp.lo tc.lo tap.lo pap.lo bintree.lo decode_simple.lo
pcd.lo prm.lo clx.lo bte.lo bx.lo fkp.lo text.lo decode_complex.lo
wvTextEngine.lo wvHtmlEngine.lo wvConfig.lo wvparse.lo reasons.lo sep.lo anlv.lo
olst.lo asumy.lo
bkd.lo bkl.lo dogrid.lo doptypography.lo pgd.lo rs.lo rr.lo tbd.lo ftxbxs.lo
wkb.lo picf.lo crc32.lo md5.lo rc4.lo decrypt97.lo decrypt95.lo twips.lo
table.lo symbol.lo mtextra.lo fopt.lo fbse.lo escher.lo bmptopng.lo basename.lo
laolareplace.lo isbidi.lo plcf.lo magick/libmagick.la libole2/libole2.la
oledecod/liboledecod.la    -lwmf -lwmflite -lfreetype -L/usr/X11R6/lib -lSM
-lICE -lX11 -lexpat -ljpeg -lpng -lz -lm -lexpat -lglib-2.0    -lpng -lz  -lm

Libtool 1.5 (libtool_1.5-1.5-alt7) invokes gcc as follows:

gcc -shared  winmmap.lo support.lo list.lo stylesheet.lo sprm.lo blip.lo utf.lo
field.lo decompresswmf.lo dop.lo roman.lo fib.lo frd.lo atrd.lo sed.lo font.lo
ffn.lo fld.lo bkf.lo dttm.lo generic.lo error.lo unicode.lo sttbf.lo xst.lo
fspa.lo fdoa.lo lst.lo lvl.lo lfo.lo filetime.lo chp.lo brc.lo anld.lo shd.lo dcs.lo
numrm.lo asumyi.lo version.lo lspd.lo phe.lo tlp.lo tc.lo tap.lo pap.lo
bintree.lo decode_simple.lo pcd.lo prm.lo clx.lo bte.lo bx.lo fkp.lo text.lo
decode_complex.lo wvTextEngine.lo wvHtmlEngine.lo wvConfig.lo wvparse.lo
reasons.lo sep.lo
anlv.lo olst.lo asumy.lo bkd.lo bkl.lo dogrid.lo doptypography.lo pgd.lo rs.lo
rr.lo tbd.lo ftxbxs.lo wkb.lo picf.lo crc32.lo md5.lo rc4.lo decrypt97.lo
decrypt95.lo twips.lo table.lo symbol.lo mtextra.lo fopt.lo fbse.lo escher.lo
bmptopng.lo basename.lo laolareplace.lo isbidi.lo plcf.lo -Wl,--whole-archive
magick/.libs/libmagick.al libole2/.libs/libole2.al oledecod/.libs/liboledecod.al
-Wl,--no-whole-archive  -L/usr/X11R6/lib -L/usr/lib magick/.libs/libmagick.al
libole2/.libs/libole2.al oledecod/.libs/liboledecod.al /usr/lib/libwmf.so
/usr/lib/libwmflite.so /usr/lib/libfreetype.so -lSM -lICE -lX11
/usr/lib/libjpeg.so /usr/lib/libexpat.so /usr/lib/libglib-2.0.so -lpng -lz -lm 
   -Wl,-soname -Wl,libwv-1.0.0 -o
.libs/libwv-1.0.0.0.0

Note the omission of the .so suffix. Libtool 1.4, when used in the same build,
doesn't drop the suffix.