A comment in tools/configure says that it is intended for these to be
command line overridable, so they shouldn't get expanded at configure
time.

The patch is fixing tools/m4/default_lib.m4 as far as I can see myself
doing this, but imo it is flawed altogether and should rather be
removed:
- setting prefix and exec_prefix to default values is being done later
  in tools/configure anyway
- setting LIB_PATH based on the (non-)existence of a lib64 directory
  underneath ${exec_prefix} is plain wrong (it can obviously exist on a
  32-bit installation)
- I wasn't able to locate any use of LIB_PATH
(I did see IanC's comment in c/s 25594:ad08cd8e7097 that removing it
supposedly causes other problems, but I don't see how that would
happen).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

---
This will require tools/configure to be re-generated.

--- a/config/Tools.mk.in
+++ b/config/Tools.mk.in
@@ -1,5 +1,6 @@
 # Prefix and install folder
-PREFIX              := @prefix@
+prefix              := @prefix@
+PREFIX              := $(prefix)
 exec_prefix         := @exec_prefix@
 LIBDIR              := @libdir@
 
--- a/tools/m4/default_lib.m4
+++ b/tools/m4/default_lib.m4
@@ -1,14 +1,19 @@
 AC_DEFUN([AX_DEFAULT_LIB],
-[AS_IF([test "\${exec_prefix}/lib" = "$libdir"],
-    [AS_IF([test "$exec_prefix" = "NONE" && test "$prefix" != "NONE"],
-        [exec_prefix=$prefix])
-    AS_IF([test "$exec_prefix" = "NONE"], [exec_prefix=$ac_default_prefix])
-    AS_IF([test -d "${exec_prefix}/lib64"], [
+[AS_IF([test "\${exec_prefix}/lib" = "$libdir"], [
+    AS_IF([test "$prefix" = "NONE"], [prefix=$ac_default_prefix])
+    AS_IF([test "$exec_prefix" = "NONE"], [exec_prefix='${prefix}'])
+    AS_IF([eval test -d "${exec_prefix}/lib64"], [
         LIB_PATH="lib64"
     ],[
         LIB_PATH="lib"
     ])
 ], [
     LIB_PATH="${libdir:`expr length "$exec_prefix" + 1`}"
+    AS_IF([test -z "${libdir##\$\{exec_prefix\}/*}"], [
+        LIB_PATH="${libdir:15}"
+    ])
+    AS_IF([test -z "${libdir##\$exec_prefix/*}"], [
+        LIB_PATH="${libdir:13}"
+    ])
 ])
 AC_SUBST(LIB_PATH)])