--enable-debug isn't listed in './configure --help' but it seems it's a recognized option (or if it isn't then it should be removed from the summary at the end of configure).
If configured without --enable-man no error is given but 'make' will fail. So it should be enabled by default.
Actually 'make' works without --enable-man but 'make install' fails with:
Making install in man
make[1]: Entering directory `/home/first/src/lxappearance/man'
Warning: you need to run configure with '--enable-man'
in order to regenerate man pages.
make[2]: Entering directory `/home/first/src/lxappearance/man'
make[2]: Nothing to be done for `install-exec-am'.
Warning: you need to run configure with '--enable-man'
in order to regenerate man pages.
test -z "/usr/share/man/man1" || /usr/bin/mkdir -p "/usr/share/man/man1"
/usr/bin/install -c -m 644 ./lxappearance.1 '/usr/share/man/man1'
/usr/bin/install: cannot stat `./lxappearance.1': No such file or directory
make[2]: *** [install-man1] Error 1
make[2]: Leaving directory `/home/first/src/lxappearance/man'
make[1]: *** [install-am] Error 2
make[1]: Leaving directory `/home/first/src/lxappearance/man'
make: *** [install-recursive] Error 1
Also 'configure --help' has conflicting information regarding this option:
.
--enable-man regenerate roff man pages from Docbook [default=yes] <<<<
--enable-more-warnings Add more warnings [default=no]
--enable-gtk3 enable to use gtk-3.0 instead of gtk-2.0
--enable-dbus Use Dbus support (usefull for lxsession > 0.4.9)
[default=no]
--enable-man regenerate roff man pages from Docbook [default=no] <<<<
The default is, in fact, set to 'no'.
.
Installation without --enable-man works if you use tarball (because tarball contains prebuilt man page) but does not if you use GIT sources. Can that satisfy you? Thank you very much.