Normally the configure script would detect and enable features if available,
this should be reported as a bug upstream.

You could also detect if aspell is installed or not, and provide --disable-
aspell if its not, for example:

...
build() {
        # Detect if aspell is available
        if [ -f /usr/include/aspell.h ]; then
                aspell=y
        else
                aspell=n
        fi

        cd $name-$version
        ./configure \
                --prefix=/usr \
                "$([ $aspell = y ] || echo --disable-aspell)"
...

I noticed you forcefully disable other things that are correctly detected and
enabled by the configure script, such as meanwhile.  This is in fact the
reason why I created my own port for pidgin.