Merge pull request swiftlang#10704 from chelcassanova/cherry/6.2/fix-cmake4-macos-build

[lldb][cmake] Error out when building debugserver with CMake 4

Author: JDevlieghere

lldb/tools/debugserver/source/CMakeLists.txt

@@ -154,6 +154,21 @@ endif()
 
 add_definitions(-DLLDB_USE_OS_LOG)
 
+# Make sure we have the macOS SDK root as mig needs it and will silently
+# fail to generate its output files without it.
+if(CMAKE_OSX_SYSROOT)
+  set(MIG_SYSROOT ${CMAKE_OSX_SYSROOT})
+else()
+  execute_process(COMMAND xcrun --show-sdk-path
+    OUTPUT_VARIABLE MIG_SYSROOT
+    ERROR_QUIET
+    OUTPUT_STRIP_TRAILING_WHITESPACE)
+endif()
+
+if(NOT MIG_SYSROOT)
+  message(FATAL_ERROR "Unable to obtain sysroot required by mig (Mach Interface Generator). Set CMAKE_OSX_SYSROOT to explicitly specify a sysroot.")
+endif()
+
 if(${CMAKE_OSX_SYSROOT} MATCHES ".Internal.sdk$")
   message(STATUS "LLDB debugserver energy support is enabled")
   add_definitions(-DLLDB_ENERGY)
@@ -177,7 +192,7 @@ endif()
 separate_arguments(MIG_ARCH_FLAGS_SEPARTED NATIVE_COMMAND "${MIG_ARCH_FLAGS}")
 
 add_custom_command(OUTPUT ${generated_mach_interfaces}
-  VERBATIM COMMAND mig ${MIG_ARCH_FLAGS_SEPARTED} -isysroot ${CMAKE_OSX_SYSROOT} ${CMAKE_CURRENT_SOURCE_DIR}/MacOSX/dbgnub-mig.defs
+  VERBATIM COMMAND mig ${MIG_ARCH_FLAGS_SEPARTED} -isysroot ${MIG_SYSROOT} ${CMAKE_CURRENT_SOURCE_DIR}/MacOSX/dbgnub-mig.defs
   DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/MacOSX/dbgnub-mig.defs
   )