Prevent libtool from moving flags

Hi!

I have a library that, when loading, invokes functions in the main application.  So dependencies are really resolved in reverse: the main program does not "need" the libraries, it is the libraries that use the main program to inform it that they are there.

In such a case, some distros, such as Ubuntu, will completely drop the dependency on the library.  The workaround is well known: use -Wl,--no-as-needed.

Unfortunately, libtool moves the options around, and since -Wl,--(no-)?-as-needed applies to the libraries that are _after_ it, the result is disastrous:

# ./libtool --tag=CXX --mode=link g++-4.9 -Xlinker --no-as-needed -Wl,--no-as-needed -g -O2 -std=c++14 -avoid-version -module -L/usr/lib/python3.4/config-3.4m-x86_64-linux-gnu -L/usr/lib -lpthread -ldl  -lutil -lm  -lpython3.4m -Xlinker -export-dynamic -Wl,-O1 -Wl,-Bsymbolic-functions -o python/vcsn_cxx.la -rpath /usr/local/lib/python3.4/site-packages python/python_vcsn_cxx_la-vcsn_cxx.lo -lboost_python-py34 -lpthread -ldl  -lutil -lm  -lpython3.4m lib/liblal_char_b.la  lib/liblal_char_q.la  lib/liblal_char_z.la lib/libvcsn.la
libtool: warning: '/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/libltdl.la' seems to be moved
libtool: link: rm -fr  python/.libs/vcsn_cxx.la python/.libs/vcsn_cxx.lai python/.libs/vcsn_cxx.so
libtool: link: g++-4.9  -fPIC -DPIC -shared -nostdlib /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.9/crtbeginS.o  python/.libs/python_vcsn_cxx_la-vcsn_cxx.o   -Wl,-rpath -Wl,/build/vcsn/_build/lib/.libs -Wl,-rpath -Wl,/usr/local/lib/vcsn -L/usr/lib/python3.4/config-3.4m-x86_64-linux-gnu -L/usr/lib -lboost_python-py34 -lpthread -lutil -lpython3.4m lib/.libs/liblal_char_b.so lib/.libs/liblal_char_q.so lib/.libs/liblal_char_z.so lib/.libs/libvcsn.so -L/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu -lboost_filesystem -lboost_system /usr/lib/x86_64-linux-gnu/libltdl.so -ldl -lrt -L/usr/lib/gcc/x86_64-linux-gnu/4.9 -L/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib -L/lib/x86_64-linux-gnu -L/lib/../lib -L/usr/lib/x86_64-linux-gn
 u -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.9/../../.. -lstdc++ -lm -lc -lgcc_s /usr/lib/gcc/x86_64-linux-gnu/4.9/crtendS.o /usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crtn.o  -Wl,--no-as-needed -Wl,--no-as-needed -g -O2 -Wl,-export-dynamic -Wl,-O1 -Wl,-Bsymbolic-functions   -pthread -Wl,-soname -Wl,vcsn_cxx.so -o python/.libs/vcsn_cxx.so
libtool: link: ( cd "python/.libs" && rm -f "vcsn_cxx.la" && ln -s "../vcsn_cxx.la" "vcsn_cxx.la" )

So basically:

$ libtool --tag=CXX --mode=link g++-4.9 -Wl,--no-as-needed lib/liblal_char_b.la ...

becomes

$ g++-4.9 lib/liblal_char_b.la...  -Wl,--no-as-needed

so -Wl,--no-as-needed has no effects, it is too late.

I have read the faq, and I do know that there is a workaround: "./configure CXX='g++ -Wl,--no-as-needed'", and yes it works.  But I meant to say that it would be nice if options could stay where they are :)

Cheers!
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