Currently the `conda-shell` binary is installed as
`conda-shell-4.6.14` which is not very friendly to type.

With this change the binary is simply installed as `conda-shell`.

branch names are mutable, and with
NixOS/systemd#29 being merged in, the nixos-v242
branch advanced from 5c20aab77900f478fd380ab189787d80e4a35963 to
40eb070cb309ec09def0ecdeaf7514c702200835, causing systemd's
fetchFromGitHub to fail with a sha256sum mismatch (when not relying on
the cache).

Fix this, by pointing systemd.src to the commit id before the branch
advancement. This won't cause a rebuild, as the sha256 stayed the same.

Fast-forwarding systemd to 40eb070cb309ec09def0ecdeaf7514c702200835 will
be done in NixOS/nixpkgs#63784 , which also uses
the commit id, and not a branch name for rev.

See NixOS/nixpkgs#56245

Testing: 0 ..
FAIL: LLVM-Unit :: tools/llvm-exegesis/./LLVMExegesisTests/PerfHelperTest.FunctionalTest (2933 of 27000)
******************** TEST 'LLVM-Unit :: tools/llvm-exegesis/./LLVMExegesisTests/PerfHelperTest.FunctionalTest' FAILED ********************
Note: Google Test filter = PerfHelperTest.FunctionalTest
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from PerfHelperTest
[ RUN      ] PerfHelperTest.FunctionalTest
/build/llvm/unittests/tools/llvm-exegesis/PerfHelperTest.cpp:37: Failure
      Expected: CallbackEventName
            Which is: ""
            To be equal to: "CYCLES:u"
            /build/llvm/unittests/tools/llvm-exegesis/PerfHelperTest.cpp:38: Failure
            Value of: CallbackEventNameFullyQualifed
            Expected: isn't empty
              Actual: ""
              [  FAILED  ] PerfHelperTest.FunctionalTest (3 ms)
              [----------] 1 test from PerfHelperTest (3 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (3 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] PerfHelperTest.FunctionalTest

 1 FAILED TEST
 invalid event attribute - cannot create event CYCLES:u

********************
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..

1 warning(s) in tests.
Testing Time: 108.19s
********************
Failing Tests (1):
    LLVM-Unit :: tools/llvm-exegesis/./LLVMExegesisTests/PerfHelperTest.FunctionalTest

  Expected Passes    : 25609
    Expected Failures  : 141
      Unsupported Tests  : 1249
        Unexpected Failures: 1
        make[3]: *** [CMakeFiles/check-all.dir/build.make:58: CMakeFiles/check-all] Error 1
        make[3]: Leaving directory '/build/llvm/build'
        make[2]: *** [CMakeFiles/Makefile2:365: CMakeFiles/check-all.dir/all] Error 2
        make[2]: Leaving directory '/build/llvm/build'
        make[1]: *** [CMakeFiles/Makefile2:372: CMakeFiles/check-all.dir/rule] Error 2
        make[1]: Leaving directory '/build/llvm/build'
        make: *** [Makefile:251: check-all] Error 2
        builder for '/nix/store/4kq72x6ahrigryr6yjjj7c7ayqy8z2sl-llvm-7.0.1.drv' failed with exit code 2Testing: 0 ..
        FAIL: LLVM-Unit :: tools/llvm-exegesis/./LLVMExegesisTests/PerfHelperTest.FunctionalTest (2933 of 27000)
        ******************** TEST 'LLVM-Unit :: tools/llvm-exegesis/./LLVMExegesisTests/PerfHelperTest.FunctionalTest' FAILED ********************
        Note: Google Test filter = PerfHelperTest.FunctionalTest
        [==========] Running 1 test from 1 test case.
        [----------] Global test environment set-up.
        [----------] 1 test from PerfHelperTest
        [ RUN      ] PerfHelperTest.FunctionalTest
        /build/llvm/unittests/tools/llvm-exegesis/PerfHelperTest.cpp:37: Failure
              Expected: CallbackEventName
                    Which is: ""
                    To be equal to: "CYCLES:u"
                    /build/llvm/unittests/tools/llvm-exegesis/PerfHelperTest.cpp:38: Failure
                    Value of: CallbackEventNameFullyQualifed
                    Expected: isn't empty
                      Actual: ""
                      [  FAILED  ] PerfHelperTest.FunctionalTest (3 ms)
                      [----------] 1 test from PerfHelperTest (3 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (3 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] PerfHelperTest.FunctionalTest

 1 FAILED TEST
 invalid event attribute - cannot create event CYCLES:u

********************
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..

1 warning(s) in tests.
Testing Time: 108.19s
********************
Failing Tests (1):
    LLVM-Unit :: tools/llvm-exegesis/./LLVMExegesisTests/PerfHelperTest.FunctionalTest

  Expected Passes    : 25609
    Expected Failures  : 141
      Unsupported Tests  : 1249
        Unexpected Failures: 1
        make[3]: *** [CMakeFiles/check-all.dir/build.make:58: CMakeFiles/check-all] Error 1
        make[3]: Leaving directory '/build/llvm/build'
        make[2]: *** [CMakeFiles/Makefile2:365: CMakeFiles/check-all.dir/all] Error 2
        make[2]: Leaving directory '/build/llvm/build'
        make[1]: *** [CMakeFiles/Makefile2:372: CMakeFiles/check-all.dir/rule] Error 2
        make[1]: Leaving directory '/build/llvm/build'
        make: *** [Makefile:251: check-all] Error 2
        builder for '/nix/store/4kq72x6ahrigryr6yjjj7c7ayqy8z2sl-llvm-7.0.1.drv' failed with exit code 2

When $subPackages has more than one item, the build was failing because
./ was added only to the first subPackage. This commit adds ./ to all
specified subPackages.

conda: Remove version suffix

systemd: point to commit id instead of branch name

pythonPackages.django_taggit: fix build, enable tests