From f21ae77a0174c9ced5e61dc2b1df6499e71fe930 Mon Sep 17 00:00:00 2001
From: Nadia Holmquist Pedersen <nadia@nhp.sh>
Date: Fri, 23 Jul 2021 06:31:20 +0200
Subject: [PATCH] Allow for using LLVM from Homebrew and include its libc++

---
 CMakeLists.txt                      |  6 ++++--
 cmake/Toolchain-Homebrew-LLVM.cmake | 12 ++++++++++++
 tools/mac-libs.rb                   |  7 ++++++-
 3 files changed, 22 insertions(+), 3 deletions(-)
 create mode 100644 cmake/Toolchain-Homebrew-LLVM.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 242193e0..81fb0acf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -123,8 +123,10 @@ if (ENABLE_LTO)
 		if (NOT LLD STREQUAL "LLD-NOTFOUND")
 			add_link_options(-fuse-ld=lld)
 		endif()
-		set(CMAKE_AR "llvm-ar")
-		set(CMAKE_RANLIB "llvm-ranlib")
+		if (NOT APPLE)
+			set(CMAKE_AR "llvm-ar")
+			set(CMAKE_RANLIB "llvm-ranlib")
+		endif()
 	endif()
 endif()
 
diff --git a/cmake/Toolchain-Homebrew-LLVM.cmake b/cmake/Toolchain-Homebrew-LLVM.cmake
new file mode 100644
index 00000000..15b6d24d
--- /dev/null
+++ b/cmake/Toolchain-Homebrew-LLVM.cmake
@@ -0,0 +1,12 @@
+# Toolchain file for building with Homebrew's LLVM on macOS
+# This is useful on 10.14 where std::filesystem is not supported.
+
+set(CMAKE_C_COMPILER /usr/local/opt/llvm/bin/clang)
+set(CMAKE_CXX_COMPILER /usr/local/opt/llvm/bin/clang++)
+
+add_link_options(-L/usr/local/opt/llvm/lib)
+
+# LLVM in Homebrew is built with latest Xcode which has a newer linker than
+# what is bundled in the default install of Xcode Command Line Tools, so we
+# override it to prevent it passing flags not supported by the system's ld.
+add_link_options(-mlinker-version=450)
diff --git a/tools/mac-libs.rb b/tools/mac-libs.rb
index 534b003a..94e33f44 100755
--- a/tools/mac-libs.rb
+++ b/tools/mac-libs.rb
@@ -56,6 +56,10 @@ def expand_load_path(lib, path)
         file = $fallback_rpaths
           .map { |it| File.join(it, file_name) }
           .find { |it| File.exist? it }
+	if file == nil
+          path = File.join(File.dirname(lib), file_name)
+          file = path if File.exist? path
+        end
         return file, :rpath if file
       when "executable_path"
         file = File.join(File.dirname(executable), file_name)
@@ -85,7 +89,6 @@ def install_name_tool(exec, action, path1, path2 = nil)
   args = ["-#{action.to_s}", path1]
   args << path2 if path2 != nil
 
-  FileUtils.chmod("u+w", exec)
   out, status = Open3.capture2e("install_name_tool", *args, exec)
   if status != 0
     puts out
@@ -129,6 +132,7 @@ def fixup_libs(prog, orig_path)
       next if File.exist? File.join(frameworks_dir, fwname)
       expath, _ = expand_load_path(orig_path, framework)
       FileUtils.cp_r(expath, frameworks_dir, preserve: true)
+      FileUtils.chmod_R("u+w", File.join(frameworks_dir, fwname))
       fixup_libs File.join(frameworks_dir, fwname, fwlib), libpath
     else
       libname = File.basename(libpath)
@@ -141,6 +145,7 @@ def fixup_libs(prog, orig_path)
       next if File.exist? dest
       expath, _ = expand_load_path(orig_path, libpath)
       FileUtils.copy expath, frameworks_dir
+      FileUtils.chmod("u+w", dest)
       fixup_libs dest, libpath
     end
   end