build: sync ax_boost_base from upstream

I upstreamed our change,
https://github.com/autoconf-archive/autoconf-archive/pull/260, so sync
with upstream.

Slightly simplifies #25465.

build-aux/m4/ax_boost_base.m4

@@ -11,9 +11,9 @@
 #   Test for the Boost C++ libraries of a particular version (or newer)
 #
 #   If no path to the installed boost library is given the macro searchs
-#   under /usr, /usr/local, /opt, /opt/local and /opt/homebrew and evaluates the
-#   $BOOST_ROOT environment variable. Further documentation is available at
-#   <http://randspringer.de/boost/index.html>.
+#   under /usr, /usr/local, /opt, /opt/local and /opt/homebrew and evaluates
+#   the $BOOST_ROOT environment variable. Further documentation is available
+#   at <http://randspringer.de/boost/index.html>.
 #
 #   This macro calls:
 #
@@ -33,7 +33,7 @@
 #   and this notice are preserved. This file is offered as-is, without any
 #   warranty.
 
-#serial 48
+#serial 51
 
 # example boost program (need to pass version)
 m4_define([_AX_BOOST_BASE_PROGRAM],
@@ -114,7 +114,7 @@ AC_DEFUN([_AX_BOOST_BASE_RUNDETECT],[
     AS_CASE([${host_cpu}],
       [x86_64],[libsubdirs="lib64 libx32 lib lib64"],
       [mips*64*],[libsubdirs="lib64 lib32 lib lib64"],
-      [ppc64|powerpc64|s390x|sparc64|aarch64|ppc64le|powerpc64le|riscv64],[libsubdirs="lib64 lib lib64"],
+      [ppc64|powerpc64|s390x|sparc64|aarch64|ppc64le|powerpc64le|riscv64|e2k],[libsubdirs="lib64 lib lib64"],
       [libsubdirs="lib"]
     )
 
@@ -128,7 +128,7 @@ AC_DEFUN([_AX_BOOST_BASE_RUNDETECT],[
     )
 
     dnl first we check the system location for boost libraries
-    dnl this location ist chosen if boost libraries are installed with the --layout=system option
+    dnl this location is chosen if boost libraries are installed with the --layout=system option
     dnl or if you install boost with RPM
     AS_IF([test "x$_AX_BOOST_BASE_boost_path" != "x"],[
         AC_MSG_CHECKING([for boostlib >= $1 ($WANT_BOOST_VERSION) includes in "$_AX_BOOST_BASE_boost_path/include"])
@@ -151,7 +151,7 @@ AC_DEFUN([_AX_BOOST_BASE_RUNDETECT],[
         else
             search_libsubdirs="$multiarch_libsubdir $libsubdirs"
         fi
-        for _AX_BOOST_BASE_boost_path_tmp in /usr /usr/local /opt /opt/local /opt/homebrew/; do
+        for _AX_BOOST_BASE_boost_path_tmp in /usr /usr/local /opt /opt/local /opt/homebrew ; do
             if test -d "$_AX_BOOST_BASE_boost_path_tmp/include/boost" && test -r "$_AX_BOOST_BASE_boost_path_tmp/include/boost" ; then
                 for libsubdir in $search_libsubdirs ; do
                     if ls "$_AX_BOOST_BASE_boost_path_tmp/$libsubdir/libboost_"* >/dev/null 2>&1 ; then break; fi