0003-revert-monorepo-requirement.patch

Upstream commit 8c03fdf34a659925a3f09c8f54016e47ea1c7519 changed the build such
that it requires living inside the monorepo with libcxx available, only so that
it can reuse a CMake file to simplify some build steps. This patch is a revert
of that commit applied only to libunwind.

---
diff --git a/libunwind/CMakeLists.txt b/libunwind/CMakeLists.txt
index 570b8db90653..a383d7d77d6f 100644
--- a/libunwind/CMakeLists.txt
+++ b/libunwind/CMakeLists.txt
@@ -1,7 +1,3 @@
-if (NOT IS_DIRECTORY "${CMAKE_CURRENT_LIST_DIR}/../libcxx")
-  message(FATAL_ERROR "libunwind requires being built in a monorepo layout with libcxx available")
-endif()
-
 #===============================================================================
 # Setup Project
 #===============================================================================
@@ -15,31 +11,103 @@ set(CMAKE_MODULE_PATH
   ${CMAKE_MODULE_PATH}
   )
 
-set(LIBUNWIND_SOURCE_DIR  ${CMAKE_CURRENT_SOURCE_DIR})
-set(LIBUNWIND_BINARY_DIR  ${CMAKE_CURRENT_BINARY_DIR})
-set(LIBUNWIND_LIBCXX_PATH "${CMAKE_CURRENT_LIST_DIR}/../libcxx" CACHE PATH
-        "Specify path to libc++ source.")
-
 if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR OR LIBUNWIND_STANDALONE_BUILD)
   project(libunwind LANGUAGES C CXX ASM)
 
+  # Rely on llvm-config.
+  set(CONFIG_OUTPUT)
+  if(NOT LLVM_CONFIG_PATH)
+    find_program(LLVM_CONFIG_PATH "llvm-config")
+  endif()
+  if (DEFINED LLVM_PATH)
+    set(LLVM_INCLUDE_DIR ${LLVM_INCLUDE_DIR} CACHE PATH "Path to llvm/include")
+    set(LLVM_PATH ${LLVM_PATH} CACHE PATH "Path to LLVM source tree")
+    set(LLVM_MAIN_SRC_DIR ${LLVM_PATH})
+    set(LLVM_CMAKE_PATH "${LLVM_PATH}/cmake/modules")
+  elseif(LLVM_CONFIG_PATH)
+    message(STATUS "Found LLVM_CONFIG_PATH as ${LLVM_CONFIG_PATH}")
+    set(CONFIG_COMMAND ${LLVM_CONFIG_PATH} "--includedir" "--prefix" "--src-root")
+    execute_process(COMMAND ${CONFIG_COMMAND}
+                    RESULT_VARIABLE HAD_ERROR
+                    OUTPUT_VARIABLE CONFIG_OUTPUT)
+    if (NOT HAD_ERROR)
+      string(REGEX REPLACE "[ \t]*[\r\n]+[ \t]*" ";"
+             CONFIG_OUTPUT ${CONFIG_OUTPUT})
+    else()
+      string(REPLACE ";" " " CONFIG_COMMAND_STR "${CONFIG_COMMAND}")
+      message(STATUS "${CONFIG_COMMAND_STR}")
+      message(FATAL_ERROR "llvm-config failed with status ${HAD_ERROR}")
+    endif()
+
+    list(GET CONFIG_OUTPUT 0 INCLUDE_DIR)
+    list(GET CONFIG_OUTPUT 1 LLVM_OBJ_ROOT)
+    list(GET CONFIG_OUTPUT 2 MAIN_SRC_DIR)
+
+    set(LLVM_INCLUDE_DIR ${INCLUDE_DIR} CACHE PATH "Path to llvm/include")
+    set(LLVM_BINARY_DIR ${LLVM_OBJ_ROOT} CACHE PATH "Path to LLVM build tree")
+    set(LLVM_MAIN_SRC_DIR ${MAIN_SRC_DIR} CACHE PATH "Path to LLVM source tree")
+    set(LLVM_LIT_PATH "${LLVM_PATH}/utils/lit/lit.py")
+
+    # --cmakedir is supported since llvm r291218 (4.0 release)
+    execute_process(
+      COMMAND ${LLVM_CONFIG_PATH} --cmakedir
+      RESULT_VARIABLE HAD_ERROR
+      OUTPUT_VARIABLE CONFIG_OUTPUT
+      ERROR_QUIET)
+    if(NOT HAD_ERROR)
+      string(STRIP "${CONFIG_OUTPUT}" LLVM_CMAKE_PATH_FROM_LLVM_CONFIG)
+      file(TO_CMAKE_PATH "${LLVM_CMAKE_PATH_FROM_LLVM_CONFIG}" LLVM_CMAKE_PATH)
+    else()
+      file(TO_CMAKE_PATH "${LLVM_BINARY_DIR}" LLVM_BINARY_DIR_CMAKE_STYLE)
+      set(LLVM_CMAKE_PATH "${LLVM_BINARY_DIR_CMAKE_STYLE}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
+    endif()
+  else()
+    message(WARNING "UNSUPPORTED LIBUNWIND CONFIGURATION DETECTED: "
+                    "llvm-config not found and LLVM_MAIN_SRC_DIR not defined. "
+                    "Reconfigure with -DLLVM_CONFIG=path/to/llvm-config "
+                    "or -DLLVM_PATH=path/to/llvm-source-root.")
+  endif()
+
+  if (EXISTS ${LLVM_CMAKE_PATH})
+    list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_PATH}")
+    include("${LLVM_CMAKE_PATH}/AddLLVM.cmake")
+    include("${LLVM_CMAKE_PATH}/HandleLLVMOptions.cmake")
+  else()
+    message(WARNING "Not found: ${LLVM_CMAKE_PATH}")
+  endif()
+
   set(PACKAGE_NAME libunwind)
   set(PACKAGE_VERSION 12.0.1)
   set(PACKAGE_STRING "${PACKAGE_NAME} ${PACKAGE_VERSION}")
   set(PACKAGE_BUGREPORT "llvm-bugs@lists.llvm.org")
 
-  # Add the CMake module path of libcxx so we can reuse HandleOutOfTreeLLVM.cmake
-  set(LIBUNWIND_LIBCXX_CMAKE_PATH "${LIBUNWIND_LIBCXX_PATH}/cmake/Modules")
-  list(APPEND CMAKE_MODULE_PATH "${LIBUNWIND_LIBCXX_CMAKE_PATH}")
+  if (EXISTS ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py)
+    set(LLVM_LIT ${LLVM_MAIN_SRC_DIR}/utils/lit/lit.py)
+  else()
+    # Seek installed Lit.
+    find_program(LLVM_LIT "lit.py" ${LLVM_MAIN_SRC_DIR}/utils/lit
+                 DOC "Path to lit.py")
+  endif()
 
-  # In a standalone build, we don't have llvm to automatically generate the
-  # llvm-lit script for us.  So we need to provide an explicit directory that
-  # the configurator should write the script into.
-  set(LIBUNWIND_STANDALONE_BUILD 1)
-  set(LLVM_LIT_OUTPUT_DIR "${LIBUNWIND_BINARY_DIR}/bin")
+  if (LLVM_LIT)
+    # Define the default arguments to use with 'lit', and an option for the user
+    # to override.
+    set(LIT_ARGS_DEFAULT "-sv")
+    if (MSVC OR XCODE)
+      set(LIT_ARGS_DEFAULT "${LIT_ARGS_DEFAULT} --no-progress-bar")
+    endif()
+    set(LLVM_LIT_ARGS "${LIT_ARGS_DEFAULT}" CACHE STRING "Default options for lit")
+
+    # On Win32 hosts, provide an option to specify the path to the GnuWin32 tools.
+    if (WIN32 AND NOT CYGWIN)
+      set(LLVM_LIT_TOOLS_DIR "" CACHE PATH "Path to GnuWin32 tools")
+    endif()
+  else()
+    set(LLVM_INCLUDE_TESTS OFF)
+  endif()
 
-  # Find the LLVM sources and simulate LLVM CMake options.
-  include(HandleOutOfTreeLLVM)
+  set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX})
+  set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX})
 else()
   set(LLVM_LIT "${CMAKE_SOURCE_DIR}/utils/lit/lit.py")
 endif()
@@ -85,8 +153,6 @@ set(LIBUNWIND_TEST_COMPILER_FLAGS "" CACHE STRING
     "Additional compiler flags for test programs.")
 set(LIBUNWIND_TEST_CONFIG "${CMAKE_CURRENT_SOURCE_DIR}/test/lit.site.cfg.in" CACHE STRING
     "The Lit testing configuration to use when running the tests.")
-set(LIBUNWIND_TEST_PARAMS "" CACHE STRING
-    "A list of parameters to run the Lit test suite with.")
 
 if (NOT LIBUNWIND_ENABLE_SHARED AND NOT LIBUNWIND_ENABLE_STATIC)
   message(FATAL_ERROR "libunwind must be built as either a shared or static library.")
@@ -113,6 +179,9 @@ set(CMAKE_MODULE_PATH
     "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
     ${CMAKE_MODULE_PATH})
 
+set(LIBUNWIND_SOURCE_DIR  ${CMAKE_CURRENT_SOURCE_DIR})
+set(LIBUNWIND_BINARY_DIR  ${CMAKE_CURRENT_BINARY_DIR})
+
 if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
   set(LIBUNWIND_LIBRARY_DIR ${LLVM_LIBRARY_OUTPUT_INTDIR}/${LLVM_DEFAULT_TARGET_TRIPLE}/c++)
   set(LIBUNWIND_INSTALL_LIBRARY_DIR lib${LLVM_LIBDIR_SUFFIX}/${LLVM_DEFAULT_TARGET_TRIPLE}/c++)