Add Process::Status#system_exit_status (#15296)

Provides a consistent, portable API to retrieve the platform-specific exit status

spec/std/process/status_spec.cr

@@ -42,6 +42,16 @@ describe Process::Status do
     status_for(:interrupted).exit_code?.should be_nil
   end
 
+  it "#system_exit_status" do
+    Process::Status.new(exit_status(0)).system_exit_status.should eq 0_u32
+    Process::Status.new(exit_status(1)).system_exit_status.should eq({{ flag?(:unix) ? 0x0100_u32 : 1_u32 }})
+    Process::Status.new(exit_status(127)).system_exit_status.should eq({{ flag?(:unix) ? 0x7f00_u32 : 127_u32 }})
+    Process::Status.new(exit_status(128)).system_exit_status.should eq({{ flag?(:unix) ? 0x8000_u32 : 128_u32 }})
+    Process::Status.new(exit_status(255)).system_exit_status.should eq({{ flag?(:unix) ? 0xFF00_u32 : 255_u32 }})
+
+    status_for(:interrupted).system_exit_status.should eq({% if flag?(:unix) %}Signal::INT.value{% else %}LibC::STATUS_CONTROL_C_EXIT{% end %})
+  end
+
   it "#success?" do
     Process::Status.new(exit_status(0)).success?.should be_true
     Process::Status.new(exit_status(1)).success?.should be_false

src/process/status.cr

@@ -108,6 +108,13 @@ class Process::Status
     @exit_status.to_i32!
   end
 
+  # Returns the exit status as indicated by the operating system.
+  #
+  # It can encode exit codes and termination signals and is platform-specific.
+  def system_exit_status : UInt32
+    @exit_status.to_u32!
+  end
+
   {% if flag?(:win32) %}
     # :nodoc:
     def initialize(@exit_status : UInt32)