POSIX threads (or pthreads) is part of glibc (not glib2), and if you want to build things against installed libraries, you need to install the development packages:
By convention, shared objects for libraries are named lib.... So the pthread library will be called libpthread.so. You can query the repositories to see which package (if any) provides the library as a capability:
Thank you for the replies. Sadly, glibc-devel was already installed, presumably because I already installed the entire “C Development Tools and Libraries” group.
# are you did this that way?
git clone https://github.com/cebix/macemu.git
cd macemu/SheepShaver
make links
cd macemu/SheepShaver/src/Unix
./autogen.sh
make
# Is this produce any output?
find / -type f -name *pthread.h 2>/dev/null
Then it’s about the build system (autotools here?) not being able to find it. This is often because it isn’t looking in the right place. Check where the various compiler and linker flags are being set. You may have to tweak those bits.