man/Makefile.am

man_MANS = cwebp.1 dwebp.1
if WANT_MUX
  man_MANS += webpmux.1
endif
if BUILD_GIF2WEBP
  man_MANS += gif2webp.1
endif
if BUILD_VWEBP
  man_MANS += vwebp.1
endif
EXTRA_DIST = $(man_MANS)