Fix cache handling

build/autotools/includes/acinclude.m4

@@ -216,15 +216,18 @@ dnl @summary check whether compiler requires -rpath for libstdc++.so
 AC_DEFUN([CXX_RPATH_CHECK],
 [
   AC_CACHE_CHECK([whether the compiler requires -rpath], ax_cv_prog_cc_rpath, [
-    ax_cv_prog_cc_rpath=
+    ax_cv_prog_cc_rpath=no
     for path in `${CXX} -print-search-dirs | awk '/^libraries:/ {print substr([$]0, 13)}' | tr ':' ' '`; do
       if [[ -r "${path}/libstdc++.so" ]]; then
         ax_cv_prog_cc_rpath="${path}"
-        LDFLAGS="${LDFLAGS}${LDFLAGS:+ }-Wl,-rpath,${path}"
         break
       fi
     done
   ])
+
+  if [ "${ax_cv_prog_cc_rpath}" != "no" ]; then
+    LDFLAGS="${LDFLAGS}${LDFLAGS:+ }-Wl,-rpath,${ax_cv_prog_cc_rpath}"
+  fi
 ])
 
 dnl  EGG_CHECK_CCSTATIC()

configure

@@ -3002,11 +3002,10 @@ if ${ax_cv_prog_cc_rpath+:} false; then :
   $as_echo_n "(cached) " >&6
 else
 
-    ax_cv_prog_cc_rpath=
+    ax_cv_prog_cc_rpath=no
     for path in `${CXX} -print-search-dirs | awk '/^libraries:/ {print substr($0, 13)}' | tr ':' ' '`; do
       if [ -r "${path}/libstdc++.so" ]; then
         ax_cv_prog_cc_rpath="${path}"
-        LDFLAGS="${LDFLAGS}${LDFLAGS:+ }-Wl,-rpath,${path}"
         break
       fi
     done
@@ -3015,6 +3014,10 @@ fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_prog_cc_rpath" >&5
 $as_echo "$ax_cv_prog_cc_rpath" >&6; }
 
+  if  "${ax_cv_prog_cc_rpath}" != "no" ; then
+    LDFLAGS="${LDFLAGS}${LDFLAGS:+ }-Wl,-rpath,${ax_cv_prog_cc_rpath}"
+  fi
+
 
 #checkpoint
 cat >confcache <<\_ACEOF