build: add check for macOS SDK version

this provides an easy way to check for a specific macOS SDK version and
with that the availability of features.

waftools/checks/generic.py

@@ -1,5 +1,6 @@
 import os
 import inflector
+from distutils.version import StrictVersion
 from waflib.ConfigSet import ConfigSet
 from waflib import Utils
 
@@ -8,7 +9,7 @@ __all__ = [
     "check_pkg_config_cflags", "check_cc", "check_statement", "check_libs",
     "check_headers", "compose_checks", "check_true", "any_version",
     "load_fragment", "check_stub", "check_ctx_vars", "check_program",
-    "check_pkg_config_datadir"]
+    "check_pkg_config_datadir", "check_macos_sdk"]
 
 any_version = None
 
@@ -186,3 +187,13 @@ def load_fragment(fragment):
     fragment_code = fp.read()
     fp.close()
     return fragment_code
+
+def check_macos_sdk(version):
+    def fn(ctx, dependency_identifier):
+        if ctx.env.MACOS_SDK_VERSION:
+            if StrictVersion(ctx.env.MACOS_SDK_VERSION) >= StrictVersion(version):
+                ctx.define(inflector.define_key(dependency_identifier), 1)
+                return True
+        return False
+
+    return fn

waftools/detections/compiler_swift.py

@@ -1,4 +1,5 @@
 import re
+import string
 import os.path
 from waflib import Utils
 from distutils.version import StrictVersion
@@ -116,9 +117,18 @@ def __find_swift_library(ctx):
 def __find_macos_sdk(ctx):
     ctx.start_msg('Checking for macOS SDK')
     sdk = __run(['xcrun', '--sdk', 'macosx', '--show-sdk-path'])
+    sdk_build_version = __run(['xcrun', '--sdk', 'macosx', '--show-sdk-build-version' ])
+
     if sdk:
         ctx.end_msg(sdk)
         ctx.env.MACOS_SDK = sdk
+
+        if sdk_build_version:
+            verRe = re.compile("(\d+)(\D+)(\d+)")
+            version_parts = verRe.search(sdk_build_version)
+            major = int(version_parts.group(1))-4
+            minor = string.ascii_lowercase.index(version_parts.group(2).lower())
+            ctx.env.MACOS_SDK_VERSION = '10.' + str(major) + '.' + str(minor)
     else:
         ctx.end_msg(False)