fix(darwin): provide compiler-rt libraries for darwin builds

.github/workflows/ci.yml

@@ -1,4 +1,7 @@
 name: Build docker images
+concurrency:
+  group: "${{github.workflow}}-${{github.ref}}"
+  cancel-in-progress: true
 on: [push, pull_request]
 
 jobs:

Dockerfile.mri.erb

@@ -107,6 +107,8 @@ RUN git clone -q --depth=1 https://github.com/tpoechtrager/osxcross.git /opt/osx
     tar -cJf MacOSX11.1.sdk.tar.xz MacOSX11.1.sdk && \
     cd /opt/osxcross && \
     UNATTENDED=1 SDK_VERSION=11.1 OSX_VERSION_MIN=10.13 USE_CLANG_AS=1 ./build.sh && \
+    ln -s /usr/bin/llvm-config-10 /usr/bin/llvm-config && \
+    ENABLE_COMPILER_RT_INSTALL=1 SDK_VERSION=11.1 ./build_compiler_rt.sh && \
     rm -rf *~ build tarballs/*
 
 RUN echo "export PATH=/opt/osxcross/target/bin:\$PATH" >> /etc/rubybashrc && \

test/rcd_test/ext/mri/rcd_test_ext.c

@@ -1,5 +1,9 @@
 #include "rcd_test_ext.h"
 
+#ifndef __has_builtin
+  #define __has_builtin(x) 0
+#endif
+
 VALUE rb_mRcdTest;
 
 static VALUE
@@ -8,9 +12,24 @@ rcdt_do_something(VALUE self)
   return rb_str_new_cstr("something has been done");
 }
 
+static VALUE
+rcdt_darwin_builtin_available_eh(VALUE self)
+{
+#if __has_builtin(__builtin_available)
+  // This version must be higher than MACOSX_DEPLOYMENT_TARGET to prevent clang from optimizing it away
+  if (__builtin_available(macOS 10.14, *)) {
+    return Qtrue;
+  }
+  return Qfalse;
+#else
+  rb_raise(rb_eRuntimeError, "__builtin_available is not defined");
+#endif
+}
+
 void
 Init_rcd_test_ext(void)
 {
   rb_mRcdTest = rb_define_module("RcdTest");
   rb_define_singleton_method(rb_mRcdTest, "do_something", rcdt_do_something, 0);
+  rb_define_singleton_method(rb_mRcdTest, "darwin_builtin_available?", rcdt_darwin_builtin_available_eh, 0);
 }

test/rcd_test/test/test_basic.rb

@@ -9,4 +9,14 @@ def test_do_something
     assert_equal "something has been done", RcdTest.do_something
   end
 
+  def test_check_darwin_compiler_rt_symbol_resolution
+    skip("jruby should not run libc-specific tests") if RUBY_ENGINE == "jruby"
+
+    if RUBY_PLATFORM.include?("darwin")
+      assert(RcdTest.darwin_builtin_available?)
+    else
+      e = assert_raises(RuntimeError) { RcdTest.darwin_builtin_available? }
+      assert_equal("__builtin_available is not defined", e.message)
+    end
+  end
 end