math/pari 2.7.5 build failure on Linux (dlsym/dlerror/dlopen)

[Matthias Ferdinand <mf+ml.pkgsrc-users%netzwerkagentursaarland.de@localhost>]

Hi,

math/pari 2.7.5 fails to build on Linux (Ubuntu 14.04, Debian 8):

    libtool: link: cc -o .libs/gp -O3 -Wall -fno-strict-aliasing -fomit-frame-pointer -I/opt/pkgsrc/work/pkgsrc/math/pari/default/.buildlink/include -I/opt/pkgsrc/work/pkgsrc/math/pari/default/.buildlink/include/ncurses -Wl,--export-dynamic -Wl,--enable-new-dtags -Wl,-rpath -Wl,/opt/pkgsrc/lib .libs/gp.o .libs/gp_init.o .libs/gp_rl.o .libs/highlvl.o .libs/whatnow.o .libs/plotport.o .libs/plotnull.o -Wl,-rpath -Wl,/opt/pkgsrc/lib -Wl,-rpath -Wl,/opt/pkgsrc/lib  -L/opt/pkgsrc/work/pkgsrc/math/pari/default/.buildlink/lib -lm /opt/pkgsrc/work/pkgsrc/math/pari/default/.buildlink/lib/libreadline.so -L../lib /opt/pkgsrc/work/pkgsrc/math/pari/default/.buildlink/lib/libncurses.so ./.libs/libpari-gmp.so /opt/pkgsrc/work/pkgsrc/math/pari/default/.buildlink/lib/libgmp.so  -Wl,-rpath -Wl,/opt/pkgsrc/work/pkgsrc/math/pari/default/.buildlink/lib -Wl,-rpath -Wl,/opt/pkgsrc/lib
=>  ./.libs/libpari-gmp.so: undefined reference to `dlsym'
=>  ./.libs/libpari-gmp.so: undefined reference to `dlerror'
=>  ./.libs/libpari-gmp.so: undefined reference to `dlopen'
    collect2: error: ld returned 1 exit status
    Makefile:125: recipe for target 'gp' failed
    gmake[2]: *** [gp] Error 1
    gmake[2]: Leaving directory '/opt/pkgsrc/work/pkgsrc/math/pari/default/pari-2.7.5/Olinux-x86_64'
    Makefile:33: recipe for target 'gp' failed
    gmake[1]: *** [gp] Error 2
    gmake[1]: Leaving directory '/opt/pkgsrc/work/pkgsrc/math/pari/default/pari-2.7.5'
    Makefile:30: recipe for target 'all' failed
    gmake: *** [all] Error 2
    *** Error code 2


Adding "-ldl" to LDFLAGS helps.

Not sure about other instances of $OPSYS, maybe something like

    .if ${OPSYS} == "Linux"
    LDFLAGS+=             -ldl
    .endif

in Makefile will help.

Regards
Matthias