To build and installt, for most environments:
./configure
make
make install

To build a native Win32 library under cygwin, use this configure:
CC='gcc -mno-cygwin' ./configure --host=mingw32 --build=mingw32 --with-iconv=no

The following is for maintainers:

Do this when you update configure.in:
./bootstrap
or:
autoreconf -v --install --force

To build a binary distribution, use the following commands:
DESTDIR="$PWD/libxls-<version>-<arch>" make install
tar cvzf libxls-<version>-<arch>.tar.gz libxls-<version>-<arch>