Merge remote-tracking branch 'origin/master' into master-rebranch

Author: swift-ci

stdlib/toolchain/CMakeLists.txt

@@ -41,6 +41,18 @@ if("Thread" IN_LIST SWIFT_RUNTIME_USE_SANITIZERS)
   list(APPEND CXX_LINK_FLAGS "-fsanitize=thread")
 endif()
 
+# Do not enforce checks for LLVM's ABI-breaking build settings.
+# The Swift runtime uses some header-only code from LLVM's ADT classes,
+# but we do not want to link libSupport into the runtime. These checks rely
+# on the presence of symbols in libSupport to identify how the code was
+# built and cause link failures for mismatches. Without linking that library,
+# we get link failures regardless, so instead, this just disables the checks.
+if(CMAKE_VERSION VERSION_LESS 3.12)
+  append("-DLLVM_DISABLE_ABI_BREAKING_CHECKS_ENFORCING=1" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+else()
+  add_compile_definitions(LLVM_DISABLE_ABI_BREAKING_CHECKS_ENFORCING=1)
+endif()
+
 
 add_subdirectory(legacy_layouts)
 add_subdirectory(Compatibility50)