Fix missing rpath on proftpd

Recent fixes for proftpd were still not correct, we still have issues with rpath for mod_auth_web and proftpd itself which uses libcap if available, error was:
    
    ======================================================================
    ERROR: setUpModule (test)
    ----------------------------------------------------------------------
    Traceback (most recent call last):
      File "/srv/slappart11/cqg/soft/1ae6b62cded47f49a2e77af2f372cf2a/parts/slapos.core-repository/slapos/testing/testcase.py", line 154, in setUpModule
        installSoftwareUrlList(cls, [software_url], debug=debug)
      File "/srv/slappart11/cqg/soft/1ae6b62cded47f49a2e77af2f372cf2a/parts/slapos.core-repository/slapos/testing/testcase.py", line 348, in installSoftwareUrlList
        raise e
    RuntimeError: /srv/slappart11/cqg/inst/test0-0/tmp/soft/728168be59c5353c6e3c6a6bc4cad052/parts/proftpd/bin/ftpdctl uses system library /lib/x86_64-linux-gnu/libcap.so.2 for libcap.so.2 /srv/slappart11/cqg/inst/test0-0/tmp/soft/728168be59c5353c6e3c6a6bc4cad052/parts/proftpd/libexec/mod_auth_web.so has some not found libraries:
    /srv/slappart11/cqg/inst/test0-0/tmp/soft/728168be59c5353c6e3c6a6bc4cad052/parts/proftpd/libexec/mod_auth_web.so: /usr/lib/x86_64-linux-gnu/libssl.so.1.1: version `OPENSSL_1_1_1' not found (required by /srv/slappart11/cqg/inst/test0-0/tmp/shared/curl/da798e87b4f10345c33fbae0a4593114/lib/libcurl.so.4)
    /srv/slappart11/cqg/inst/test0-0/tmp/soft/728168be59c5353c6e3c6a6bc4cad052/parts/proftpd/sbin/proftpd uses system library /lib/x86_64-linux-gnu/libcap.so.2 for libcap.so.2
    /srv/slappart11/cqg/inst/test0-0/tmp/soft/728168be59c5353c6e3c6a6bc4cad052/parts/proftpd/sbin/in.proftpd uses system library /lib/x86_64-linux-gnu/libcap.so.2 for libcap.so.2
    Ran 0 tests in 530.067s
    ----------------------------------------------------------------------

/reviewed-on nexedi/slapos!685

component/proftpd/buildout.cfg

@@ -29,15 +29,14 @@ configure-options =
   --enable-nls
   --enable-ctrls
   --enable-dso
+  --disable-cap
   --with-modules=mod_sftp:mod_ban
   --prefix=${buildout:parts-directory}/${:_buildout_section_name_}
 environment = 
-  CPPFLAGS=${:cppflags}
-  LDFLAGS=${:ldflags}
+  CPPFLAGS=-I${zlib:location}/include -I${openssl:location}/include
+  LDFLAGS=-L${zlib:location}/lib -Wl,-rpath=${zlib:location}/lib -L${openssl:location}/lib -Wl,-rpath=${openssl:location}/lib
   install_user=${proftpd-environment:USER}
   install_group=${proftpd-grp:GROUP}
-cppflags=-I${zlib:location}/include -I${openssl:location}/include
-ldflags=-L${zlib:location}/lib -Wl,-rpath=${zlib:location}/lib -L${openssl:location}/lib -Wl,-rpath=${openssl:location}/lib
 patch-binary = ${patch:location}/bin/patch
 patch-options = -p1
 patches =
@@ -56,14 +55,14 @@ git-executable = ${git:location}/bin/git
 [proftpd-mod_auth_web]
 recipe = plone.recipe.command
 stop-on-error = true
+# prxs does not support setting rpath, but we can "inject" -R that will be passed to libtool
 command =
   LIBTOOL=${libtool:location}/bin/libtool \
-  LDFLAGS="-Wl,-rpath=${curl:location}/lib ${proftpd:ldflags}" \
-  ${proftpd-output:prxs} -c -i \
-  -I ${curl:location}/include ${proftpd:cppflags} \
-  -L ${curl:location}/lib/ \
+  ${proftpd-output:prxs} -c -i -d \
+  -I ${curl:location}/include \
+  -L '${curl:location}/lib/ -R ${openssl:location}/lib -R ${zlib:location}/lib' \
   -l curl \
-  -d ${proftpd-mod_auth_web-repository:location}/mod_auth_web.c
+  ${proftpd-mod_auth_web-repository:location}/mod_auth_web.c
 location=${proftpd:location}/libexec/mod_auth_web.so