build: Add m4 macro to assert argument is literal

Add a new m4 macro, OAC_ASSERT_LITERAL, that will fail autoconf if
the first argument is not a string literal (in the Autoconf sense
of the word).  Note that this macro will not emit any shell code;
it will either cause a fatal m4 error (with useful stack trace
to where the error occurred) or evaluate to an empty string.

Signed-off-by: Brian Barrett <[email protected]>

Author: bwbarrett

config/oac_literal.m4

@@ -0,0 +1,17 @@
+dnl -*- autoconf -*-
+dnl
+dnl Copyright (c) 2022      Amazon.com, Inc. or its affiliates.  All Rights reserved.
+dnl $COPYRIGHT$
+dnl
+dnl Additional copyrights may follow
+
+dnl OAC_ASSERT_LITERAL: Assert if first argument is not an Autoconf literal
+dnl
+dnl 1 -> Variable which must be a literal
+dnl 2 -> Argument reference string (usually an integer argument number)
+dnl
+dnl Assert that the first argument is a literal (in the Autoconf sense
+dnl of the word) Second argument is the argument number (ie, a bare
+dnl number) to make the error message easier to parse.
+AC_DEFUN([OAC_ASSERT_LITERAL],
+[AS_LITERAL_IF([$1], [], [m4_fatal([argument $2 ($1) must be a literal])])])dnl

config/opal_check_compiler_version.m4

@@ -27,8 +27,7 @@ AC_DEFUN([OPAL_CHECK_COMPILER_VERSION_ID],
 
 
 AC_DEFUN([OPAL_CHECK_COMPILER], [
-    AS_LITERAL_IF([$1], [],
-                  [m4_fatal([OPAL_CHECK_COMPILER argument must be a literal])])
+    OAC_ASSERT_LITERAL([$1], [1])dnl
     lower=m4_tolower([$1])
     AC_CACHE_CHECK([for compiler $lower], [opal_cv_compiler_$1],
     [