nixos-rebuild -I nixpkgs=~/Projects/Git/nixpkgs rebuild

build.log

building check-am
make  check-TESTS
checking whether mkfifo is declared without a macro... make[2]: Entering directory `/tmp/nix-build-libsigsegv-2.10.drv-0/libsigsegv-2.10/tests'
building check-TESTS
Test passed.
PASS: sigsegv1
Test passed.
PASS: sigsegv2
Doing SIGSEGV pass 1.
Stack overflow 1 caught.
Doing SIGSEGV pass 2.
Stack overflow 2 caught.
Test passed.
no
checking whether long double and double are the same... PASS: sigsegv3
/nix/store/k0vqprjmxybr7clvfljk13zsdjwklcch-bootstrap-tools/bin/sh: line 5:  7030 Bus error               ${dir}$tst
FAIL: stackoverflow1
no
checking whether printf supports infinite 'long double' arguments... /nix/store/k0vqprjmxybr7clvfljk13zsdjwklcch-bootstrap-tools/bin/sh: line 5:  7042 Bus error               ${dir}$tst
FAIL: stackoverflow2
===================
2 of 5 tests failed
===================
make[2]: *** [check-TESTS] Error 1
make[2]: Leaving directory `/tmp/nix-build-libsigsegv-2.10.drv-0/libsigsegv-2.10/tests'
make[1]: *** [check-am] Error 2
make[1]: Leaving directory `/tmp/nix-build-libsigsegv-2.10.drv-0/libsigsegv-2.10/tests'
make: *** [check-recursive] Error 1
builder for ‘/nix/store/4mlx4gcbl85r454asdqcc39axvbj47yy-libsigsegv-2.10.drv’ failed with exit code 2
cannot build derivation ‘/nix/store/3479faa04vs52v294nfmddyvv751pb44-stdenv.drv’: 1 dependencies couldn't be built
cannot build derivation ‘/nix/store/v4dsdl0dvjmx1i646hp6xd8whg2imvrs-nix-1.8.drv’: 1 dependencies couldn't be built
error: build of ‘/nix/store/v4dsdl0dvjmx1i646hp6xd8whg2imvrs-nix-1.8.drv’ failed
building the system configuration...
error: attribute ‘samba.enable’ at "/etc/nixos/configuration.nix":96:5 already defined at "/etc/nixos/configuration.nix":78:5
(use ‘--show-trace’ to show detailed location information)