CMake: run generate_xcode.txt only for the host platform (#71279)

Currently the test assumes that when we are testing for macOS we are
targeting the host architecture (since we need to reuse existing build
products to contain testing time) -- however there are some Apple
internal configurations in which that's not the case.

Addresses rdar://118337598

Author: edymtt

test/lit.cfg

@@ -399,6 +399,15 @@ if run_vers.endswith('-simulator'):
 else:
     run_environment=''
 
+# Parse the host triple
+(host_cpu, host_vendor, host_os, host_vers) = re.match('([^-]+)-([^-]+)-([^0-9-]+)(.*)', config.host_triple).groups()
+
+if f"{host_cpu}-{host_vendor}-{host_os}" == f"{run_cpu}-{run_vendor}-{run_os}":
+    # Ignore the version on purpose, to account for scenario
+    # in which the compiler has a different deployment target
+    # than the standard library
+    config.available_features.add('target-same-as-host')
+
 target_arch = run_cpu
 if run_os == 'openbsd' and run_cpu == 'amd64':
    target_arch = run_cpu
@@ -581,8 +590,6 @@ else:
             config.swift_driver_test_options,
         )
     )
-    # Parse the host triple.
-    (host_cpu, host_vendor, host_os, host_vers) = re.match('([^-]+)-([^-]+)-([^0-9-]+)(.*)', config.host_triple).groups()
     toolchain_lib_dir = make_path(config.swift_lib_dir, 'swift', host_os)
     config.host_build_swift = (
         "%s -target %s -g %s -I %s -L %s %s" % (

validation-test/BuildSystem/generate_xcode.test

@@ -15,3 +15,4 @@
 
 # REQUIRES: standalone_build
 # REQUIRES: OS=macosx
+# REQUIRES: target-same-as-host