macos reverted to the default shell init files in /etc, you should just need to add the block that Nix adds when it is installed:

# Nix
if [ -e '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh' ]; then
    . '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh'
fi
# End Nix

kay this fixes it

- env.NIX_CFLAGS_COMPILE = "-I${privateHeaders}/include";
+ env.NIX_CFLAGS_COMPILE = "-I${privateHeaders}/include -Wno-error=incompatible-pointer-types";

I’m also seeing these errors in the log. Are they non-fatal?

librpc/idl/auth.idl:154: error: Unable to determine origin of type `struct cli_credentials'
librpc/idl/auth.idl:154: error: Unable to determine origin of type `struct cli_credentials'
librpc/idl/winbind.idl:286: error: winbind_SamLogon: [out] argument 'validation' is not a pointer or array, skip client functions

as for harfbuzz it's blowing up in one of the tests

harfbuzz>  91/219 api - harfbuzz:test-unicode                                           OK              2.78s   12 subtests passed
harfbuzz>  92/219 api - harfbuzz:test-var-coords                                        OK              2.70s   2 subtests passed
harfbuzz>  93/219 api - harfbuzz:test-version                                           OK              2.80s   1 subtests passed
harfbuzz>  94/219 api - harfbuzz:test-ft                                                OK              2.77s   1 subtests passed
harfbuzz> ▶  95/219 /native_coretext_variations - ERROR:../test/api/test-coretext.c:97:test_native_coretext_variations: assertion failed (length != 0): (0 != 0) FAIL
harfbuzz> ▶  95/219                                                                     ERROR
harfbuzz>  95/219 api - harfbuzz:test-coretext                                          ERROR           2.82s   killed by signal 6 SIGABRT
harfbuzz> >>> MALLOC_PERTURB_=78 G_TEST_SRCDIR=/nix/var/nix/builds/nix-22984-2464162399/harfbuzz-12.3.0/test/api MSAN_OPTIONS=halt_on_error=1:abort_on_error=1:print_summary=1:print_stacktrace=1 MALLOC_CHECK_=1 LD_LIBRARY_PATH=/nix/var/nix/builds/nix-22984-2464162399/harfbuzz-12.3.0/build/src MESON_TEST_ITERATION=1 G_TEST_BUILDDIR=/nix/var/nix/builds/nix-22984-2464162399/harfbuzz-12.3.0/build/test/api G_DEBUG=gc-friendly ASAN_OPTIONS=halt_on_error=1:abort_on_error=1:print_summary=1 DYLD_LIBRARY_PATH=/nix/var/nix/builds/nix-22984-2464162399/harfbuzz-12.3.0/build/src UBSAN_OPTIONS=halt_on_error=1:abort_on_error=1:print_summary=1:print_stacktrace=1 /nix/var/nix/builds/nix-22984-2464162399/harfbuzz-12.3.0/build/test/api/test-coretext
harfbuzz>  ✀
harfbuzz> stderr:
harfbuzz> 2026-02-27 08:06:35.844 test-coretext[41120:32560076] CoreText: System LastResort not available, using built-in copy.
harfbuzz> **
harfbuzz> ERROR:../test/api/test-coretext.c:97:test_native_coretext_variations: assertion failed (length != 0): (0 != 0)
harfbuzz>
harfbuzz> (test program exited with status code -6)
harfbuzz>
harfbuzz>
harfbuzz>  96/219 api - harfbuzz:test-multithread                                       OK              2.82s   3 subtests passed
harfbuzz>  97/219 fuzzing - harfbuzz:shape-fuzzer-chunk-7                               OK              0.86s   6 subtests passed

FWIW I was building with

with (import ./. {}); {
  inherit
    hello
    ispc
    ghc
    nodejs
    boost
    ;
  inherit (qt6Packages)
    qtwebengine
    ;
}

FWIW I was building with

with (import ./. {}); {
  inherit
    hello
    ispc
    ghc
    nodejs
    boost
    ;
  inherit (qt6Packages)
    qtwebengine
    ;
}