Fix AC_REQUIRES breakage in LLVM autoconf tests.

Any Autoconf macro that uses AC_REQUIRES -- directly or indirectly --
must not be inside a plain shell "if" test; if it is, whatever code
gets pulled in by the AC_REQUIRES will also be inside that "if".
Instead of "if" we can use AS_IF, which knows how to get this right
(cf commit 01051a987).

The only immediate problem from getting this wrong was that AC_PROG_AWK
had to be run twice, once inside the "if llvm" block and once in the
main line.  However, it broke a different patch I'm about to submit
more thoroughly.

configure

@@ -4948,8 +4948,7 @@ fi
 
 
 
-if test "$with_llvm" = yes ; then
-   for ac_prog in gawk mawk nawk awk
+for ac_prog in gawk mawk nawk awk
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.
 set dummy $ac_prog; ac_word=$2
@@ -4991,6 +4990,7 @@ fi
   test -n "$AWK" && break
 done
 
+if test "$with_llvm" = yes; then :
 
 
 
@@ -9400,48 +9400,6 @@ else
 $as_echo "no, using $LN_S" >&6; }
 fi
 
-for ac_prog in gawk mawk nawk awk
-do
-  # Extract the first word of "$ac_prog", so it can be a program name with args.
-set dummy $ac_prog; ac_word=$2
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
-if ${ac_cv_prog_AWK+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  if test -n "$AWK"; then
-  ac_cv_prog_AWK="$AWK" # Let the user override the test.
-else
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
-for as_dir in $PATH
-do
-  IFS=$as_save_IFS
-  test -z "$as_dir" && as_dir=.
-    for ac_exec_ext in '' $ac_executable_extensions; do
-  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
-    ac_cv_prog_AWK="$ac_prog"
-    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
-  done
-IFS=$as_save_IFS
-
-fi
-fi
-AWK=$ac_cv_prog_AWK
-if test -n "$AWK"; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $AWK" >&5
-$as_echo "$AWK" >&6; }
-else
-  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
-$as_echo "no" >&6; }
-fi
-
-
-  test -n "$AWK" && break
-done
-
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for a thread-safe mkdir -p" >&5
 $as_echo_n "checking for a thread-safe mkdir -p... " >&6; }
 if test -z "$MKDIR_P"; then

configure.in

@@ -391,9 +391,8 @@ AC_SUBST(SUN_STUDIO_CC)
 PGAC_ARG_BOOL(with, llvm, no, [build with LLVM based JIT support],
               [AC_DEFINE([USE_LLVM], 1, [Define to 1 to build with LLVM based JIT support. (--with-llvm)])])
 AC_SUBST(with_llvm)
-if test "$with_llvm" = yes ; then
-   PGAC_LLVM_SUPPORT()
-fi
+dnl must use AS_IF here, else AC_REQUIRES inside PGAC_LLVM_SUPPORT malfunctions
+AS_IF([test "$with_llvm" = yes], [PGAC_LLVM_SUPPORT()])
 
 
 unset CFLAGS
@@ -1020,7 +1019,6 @@ AC_SUBST(install_bin)
 
 PGAC_PATH_PROGS(TAR, tar)
 AC_PROG_LN_S
-AC_PROG_AWK
 AC_PROG_MKDIR_P
 # When Autoconf chooses install-sh as mkdir -p program it tries to generate
 # a relative path to it in each makefile where it substitutes it. This clashes