[PATCH] libtool.m4: Fix AC_CHECK_PROG usage

In commit:

https://git.savannah.gnu.org/cgit/libtool.git/commit/m4/libtool.m4?id=64bef5ba65f6820cd5f88e5249324b4f5955ee25

AC_CHECK_TOOL was changed to AC_CHECK_PROG however the arguments are
different and this result is a value of ":". Change this to match the
original intent.

The lack of FILECMD was causing failures for mips64 builds as -m elf was 
being passed to LD which isn't supported on our targets.

Upstream-Status: Submitted [https://lists.gnu.org/archive/html/libtool-patches/2024-06/msg00000.html]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

Index: libtool-2.5.0/m4/libtool.m4
===================================================================
--- libtool-2.5.0.orig/m4/libtool.m4
+++ libtool-2.5.0/m4/libtool.m4
@@ -8216,7 +8216,7 @@ AC_SUBST([DLLTOOL])
 # ----------------
 # Check for a file(cmd) program that can be used to detect file type and magic
 m4_defun([_LT_DECL_FILECMD],
-[AC_CHECK_PROG([FILECMD], [file], [:])
+[AC_CHECK_PROG([FILECMD], [file], [file], [:])
 _LT_DECL([], [FILECMD], [1], [A file(cmd) program that detects file types])
 ])# _LD_DECL_FILECMD