[PR PATCH] [Closed]: Conditionally disable macOS incompatible tests

[github at samba.org]

There's a closed pull request on the Samba Samba Github repository

Conditionally disable macOS incompatible tests
https://github.com/samba-team/samba/pull/107
Description: Symbols _getgrent_r and _getpwent_r in source4/torture/local/nss_tests.c are undefined in macOS. It seems that checking HAVE_GETGRENT_R and HAVE_GETPWENT_R and conditionally disabling those tests as suggested by hirochachacha in the referenced bug allows samba on both `master` and `samba-4.7.1` to build properly on macOS/darwin.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11984

```
Linking default/source4/torture/smbtorture
clang: warning: argument unused during compilation: '-pie'
Undefined symbols for architecture x86_64:
  "_getgrent_r", referenced from:
      _test_enum_r_group in nss_tests_1.o
  "_getpwent_r", referenced from:
      _test_enum_r_passwd in nss_tests_1.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
```

Signed-off-by: Will Haley <willhy at gmail.com>