Cannot build in Nix when Z3 is installed on the host

[viktormalik]

When trying to compile DiffKemp in the Nix development environment on Fedora 41, I'm getting errors when I have Nix installed on my system.

Reproducer:

$ nix develop .#diffkemp-llvm16
nix $ mkdir build
nix $ cd build
nix $ cmake .. -GNinja -DCMAKE_BUILD_TYPE=Debug
[...]
[nix] $ ninja
[42/55] Linking CXX executable diffkemp/simpll/diffkemp-simpll
FAILED: diffkemp/simpll/diffkemp-simpll 
: && /nix/store/ihhhd1r1a2wb4ndm24rnm83rfnjw5n0z-gcc-wrapper-12.3.0/bin/g++ -fno-rtti -fpic -Wall -Wextra -g  diffkemp/simpll/CMakeFiles/simpll.dir/SimpLL.cpp.o -o diffkemp/simpll/diffkemp-simpll  -Wl,-rpath,/usr/lib64  diffkemp/simpll/libsimpll-lib.a  -lLLVM-16  /usr/lib64/libz3.so.4.13.4.0 && :
/nix/store/3z013mdl9cvpgvavpj19rbilihz4clvi-binutils-2.40/bin/ld: /nix/store/im40dz3167rw55lbg3r5p1f8n4c46x3z-llvm-16.0.6-lib/lib/libLLVM-16.so: undefined reference to `tigetnum@NCURSES6_TINFO_5.0.19991023'
/nix/store/3z013mdl9cvpgvavpj19rbilihz4clvi-binutils-2.40/bin/ld: /nix/store/im40dz3167rw55lbg3r5p1f8n4c46x3z-llvm-16.0.6-lib/lib/libLLVM-16.so: undefined reference to `del_curterm@NCURSES6_TINFO_5.0.19991023'
/nix/store/3z013mdl9cvpgvavpj19rbilihz4clvi-binutils-2.40/bin/ld: /nix/store/im40dz3167rw55lbg3r5p1f8n4c46x3z-llvm-16.0.6-lib/lib/libLLVM-16.so: undefined reference to `set_curterm@NCURSES6_TINFO_5.0.19991023'
/nix/store/3z013mdl9cvpgvavpj19rbilihz4clvi-binutils-2.40/bin/ld: /nix/store/im40dz3167rw55lbg3r5p1f8n4c46x3z-llvm-16.0.6-lib/lib/libLLVM-16.so: undefined reference to `setupterm@NCURSES6_TINFO_5.0.19991023'
/nix/store/3z013mdl9cvpgvavpj19rbilihz4clvi-binutils-2.40/bin/ld: /usr/lib64/libz3.so.4.13.4.0: undefined reference to `std::ios_base_library_init()@GLIBCXX_3.4.32'
/nix/store/3z013mdl9cvpgvavpj19rbilihz4clvi-binutils-2.40/bin/ld: /usr/lib64/libz3.so.4.13.4.0: undefined reference to `__cxa_call_terminate@CXXABI_1.3.15'
collect2: error: ld returned 1 exit status
[54/55] Building CXX object tests/unit_tests/simpll/CMakeFiles/runTests.dir/passes/UnifyMemcpyPassTest.cpp.o
ninja: build stopped: subcommand failed.

I suspect the issue is in this part: https://github.com/diffkemp/diffkemp/blob/ffe6d594d0973dc4d90d15090ef4119b34467ff8/diffkemp/simpll/CMakeLists.txt#L34-L39

We should not prefer system-wide packages over Nix ones. This causes the above error as the system-wide Z3 has apparently been built with GCC version incompatible with the one inside Nix.