Linking to statically compiled z3 needs additional libraries on Linux - z3

Question

I used CMake to compile a static version of (a fairly recent of) z3 using:
cmake -DBUILD_LIBZ3_SHARED=false -DCMAKE_INSTALL_PREFIX=/opt/z3-devel -G "Unix Makefiles" ../
Now when I statically link the library against a C++ program, say this small variation of a z3 example:
#include"z3++.h"
using namespace z3;
int main(int argc, char** argv) {
config conf;
context c(conf);
expr x = c.int_const("x");
expr y = c.int_const("y");
expr z = c.int_const("z");
goal g(c);
g.add( ((2*x)+y)+z == 4);
g.add( (x+(2*y))+z == 4);
g.add( x+y == 4);
std::cout << g << "\n";
tactic t(c, "fm");
apply_result r = t(g);
std::cout << r << "\n";
return 0;
}
via
g++ -c -I /opt/z3-devel/include -static -o main.o main.cc
g++ -static -L /opt/z3-devel/lib64 -o main main.o -lz3
I receive a long list of undefined reference linking errors. What solves the issue is to add -lgomp -pthread -lrt -ldl as additional libraries. The linker outputs the following warning:
/usr/bin/ld: /usr/lib/gcc/x86_64-redhat-linux/8/libgomp.a(target.o): in function `gomp_target_init':
(.text+0x32c): warning: Using 'dlopen' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
Nevertheless, the program runs fine on my own machine and on Starexec.
Is this combination of static and dynamic linking the best I can do? Shouldn't those libraries be already statically linked into libz3.a? I have static versions of gomp, pthread and rt available on the system.