Check if the tools to support ipo are available. If not use the standard...

Check if the tools to support ipo are available. If not use the standard versions as determined by libtool.

configure.ac

@@ -130,28 +130,28 @@ if test "$enable_ipo" = "yes"; then
    if test "$ax_cv_c_compiler_vendor" = "intel"; then
       CFLAGS="$CFLAGS -ip -ipo"
       LDFLAGS="$LDFLAGS -ipo"
-      : ${AR="xiar"}
-      : ${LD="xild"}
+      AC_CHECK_PROGS([AR], [xiar])
+      AC_CHECK_PROGS([LD], [xild])
       AC_MSG_RESULT([added Intel interprocedural optimization support])
    elif test "$ax_cv_c_compiler_vendor" = "oneapi"; then
       CFLAGS="$CFLAGS -ipo"
       LDFLAGS="$LDFLAGS -ipo"
-      : ${AR="xiar"}
-      : ${LD="xild"}
+      AC_CHECK_PROGS([AR], [xiar])
+      AC_CHECK_PROGS([LD], [xild])
       AC_MSG_RESULT([added oneapi interprocedural optimization support])
    elif test "$ax_cv_c_compiler_vendor" = "gnu"; then
       CFLAGS="$CFLAGS -flto"
       LDFLAGS="$LDFLAGS -flto"
       AX_COMPARE_VERSION($ax_cv_c_compiler_version, [ge], [5.0.0],
-                          [
-      : ${AR="gcc-ar"}
-      : ${RANLIB="gcc-ranlib"}
-                          ], [:] )
+         [
+         AC_CHECK_PROGS([AR], [gcc-ar])
+         AC_CHECK_PROGS([RANLIB], [gcc-ranlib])
+         ], [:] )
       AC_MSG_RESULT([added GCC interprocedural optimization support])
    elif test "$ax_cv_c_compiler_vendor" = "clang"; then
       CFLAGS="$CFLAGS -flto"
       LDFLAGS="$LDFLAGS -flto"
-      : ${RANLIB="llvm-ranlib"}
+      AC_CHECK_PROGS([RANLIB], [llvm-ranlib])
       AC_MSG_RESULT([added LLVM interprocedural optimization support])
    else
       AC_MSG_WARN([Compiler does not support interprocedural optimization])