title: Is it possible to define macros in makefiles conditionally?
body: <p>I'm writing a makefile that has to be compatible with both LINUX and the HP-UX operating system.  I'm aware that certain shell commands in LINUX are not compatible with HP-UX.  Consequently, I was wondering if it was possible to have macros declared conditionally so that if it was determined that the OS was HP-UX, the macro would be defined a certain way and if the OS was LINUX, it would be defined differently?</p>
  
  <pre><code>OS       = `uname`
  myOS     = Linux
  
  
  ifeq ($(OS),$(myOS))
      message = "HELLO LINUX"
  else
      message = "HELLO FOO" 
  endif
  
  all: install
  
  install:
      echo $(message)
  </code></pre>
  
  <p>I've tried using the approach above; however, it seems that ifeq determines that OS and myOS are not the same.  They should both be 'Linux', but it's outputting the else block instead.</p>