dependencies: Add a zlib system dependency for macOS

This comes pre-installed, but currently we don't have a way to detect it
without relying on pkg-config or cmake. This is only valid with the
apple clang-based compilers, as they do some special magic to get
headers.

mesonbuild/dependencies/__init__.py

@@ -20,7 +20,7 @@ from .base import (  # noqa: F401
     ExternalDependency, NotFoundDependency, ExternalLibrary, ExtraFrameworkDependency, InternalDependency,
     PkgConfigDependency, CMakeDependency, find_external_dependency, get_dep_identifier, packages, _packages_accept_language,
     DependencyFactory)
-from .dev import ValgrindDependency, gmock_factory, gtest_factory, llvm_factory
+from .dev import ValgrindDependency, gmock_factory, gtest_factory, llvm_factory, zlib_factory
 from .coarrays import coarray_factory
 from .mpi import MPIDependency
 from .scalapack import ScalapackDependency
@@ -44,6 +44,7 @@ packages.update({
     'gmock': gmock_factory,
     'llvm': llvm_factory,
     'valgrind': ValgrindDependency,
+    'zlib': zlib_factory,
 
     'boost': BoostDependency,
     'cuda': CudaDependency,

mesonbuild/dependencies/dev.py

@@ -28,6 +28,8 @@ from .base import (
     strip_system_libdirs, ConfigToolDependency, CMakeDependency, DependencyFactory,
 )
 from .misc import threads_factory
+from ..compilers.c import AppleClangCCompiler
+from ..compilers.cpp import AppleClangCPPCompiler
 
 if T.TYPE_CHECKING:
     from .. environment import Environment
@@ -449,6 +451,27 @@ class ValgrindDependency(PkgConfigDependency):
         return []
 
 
+class ZlibSystemDependency(ExternalDependency):
+
+    def __init__(self, name: str, environment: 'Environment', kwargs: T.Dict[str, T.Any]):
+        super().__init__(name, environment, kwargs)
+
+        # I'm not sure this is entirely correct. What if we're cross compiling
+        # from something to macOS?
+        if (self.env.machines[self.for_machine].is_darwin() and
+                isinstance(self.clib_compiler, (AppleClangCCompiler, AppleClangCPPCompiler))):
+            self.is_found = True
+            self.link_args = ['-lz']
+            # No need to set includes, xcode/clang will do that for us.
+
+            v, _ = self.clib_compiler.get_define('ZLIB_VERSION', '#include <zlib.h>', self.env, [], [self])
+            self.version = v.strip('"')
+
+    @staticmethod
+    def get_methods():
+        return [DependencyMethods.SYSTEM]
+
+
 llvm_factory = DependencyFactory(
     'LLVM',
     [DependencyMethods.CMAKE, DependencyMethods.CONFIG_TOOL],
@@ -469,3 +492,10 @@ gmock_factory = DependencyFactory(
     pkgconfig_class=GMockDependencyPC,
     system_class=GMockDependencySystem,
 )
+
+zlib_factory = DependencyFactory(
+    'zlib',
+    [DependencyMethods.PKGCONFIG, DependencyMethods.CMAKE, DependencyMethods.SYSTEM],
+    cmake_name='ZLIB',
+    system_class=ZlibSystemDependency,
+)