environment: separate illumos and Solaris kernels in Machines

While both kernels are derived from the OpenSolaris project of Sun, they
have diverged and code that works with one may not work with the other.
As such, we should provide different values for them. This was requested
by both Oracle and the illumos upstreams.

Fixes: #11922

docs/markdown/Reference-tables.md

@@ -175,7 +175,8 @@ Native names as returned by the `.kernel()` method.
 | netbsd  | |
 | nt      | |
 | xnu                 | Kernel of various Apple OSes    |
-| sunos | |
+| illumos             | Kernel derived from OpenSolaris by community efforts |
+| solaris             | Kernel derived from OpenSolaris by Oracle |
 | dragonfly | |
 | haiku| |
 | none                 | For e.g. bare metal embedded    |

mesonbuild/environment.py

@@ -403,12 +403,23 @@ KERNEL_MAPPINGS: T.Mapping[str, str] = {'freebsd': 'freebsd',
                                         'linux': 'linux',
                                         'cygwin': 'nt',
                                         'darwin': 'xnu',
-                                        'sunos': 'sunos',
                                         'dragonfly': 'dragonfly',
                                         'haiku': 'haiku',
                                         }
 
 def detect_kernel(system: str) -> T.Optional[str]:
+    if system == 'sunos':
+        # This needs to be /usr/bin/uname because gnu-uname could be installed and
+        # won't provide the necessary information
+        p, out, _ = Popen_safe(['/usr/bin/uname', '-o'])
+        if p.returncode != 0:
+            raise MesonException('Failed to run "/usr/bin/uname -o"')
+        out = out.lower().strip()
+        if out not in {'illumos', 'solaris'}:
+            mlog.warning(f'Got an unexpected value for kernel on a SunOS derived platform, expcted either "illumos" or "solaris", but got "{out}".'
+                         "Please open a Meson issue with the OS you're running and the value detected for your kernel.")
+            return None
+        return out
     return KERNEL_MAPPINGS.get(system, None)
 
 def detect_subsystem(system: str) -> T.Optional[str]: