Solution: add -lm to Libs.private of libzmq.pc so that the std::ceil
usage in src/decoder_allocators.cpp is satisfied during static linking
on CentOS 7.
See https://github.com/zeromq/libzmq/issues/3710 for a reproducer.
Solution: use requires.private, which pkg-config expands recursively
so that dependencies of dependencies can be linked against when
using pkg-config --static
Solution: use only Libs.private to avoid breaking application builds.
Even though Requires.private are supposed to be parsed only if
pkg-config is called with --static, the --cflags parameter is enough
to trigger the parsing, causing build failures for applications that
do not (and should not) depend on libzmq's dependencies.
Solution: add dependencies, if necessary, to the .private Libs and
Requires field of the pkgconfig file at build time.
This way pkg-config --static --libs libzmq will correctly print
dependencies if they were used to build the static libzmq.a library.
Libzmq uses C++ standard library features, so users of it should link
against that as well when statically linking.
Add it to Libs.private so users using pkg-config automatically gets the
correct linker flags.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
