bug#62896: [Configure] Bug with check for PERL when path has spaces (i.e. Windows)

[Karl Berry]

I (finally) installed this patch to quit early if the perl path has
spaces. Thanks.

As for MKDIR_P and INSTALL, I guess it is somewhere in the
prerequisite/autoconf stuff. I suppose it would be rare that they would
be found in a path with spaces while perl was not, so I think it's ok to
let that go. --best, karl.

--- a/configure.ac
+++ b/configure.ac
@@ -71,6 +71,12 @@ AC_PATH_PROG([PERL], [perl])
 if test -z "$PERL"; then
    AC_MSG_ERROR([perl not found])
 fi
+if test x"`echo $PERL | grep ' '`" != "x"; then
+  AC_MSG_ERROR([The path to your Perl contains spaces.
+This would cause build failures later or unusable programs.
+Please use a path without spaces and try again.])
+fi
+
 # Save details about the selected perl interpreter in config.log.
 AM_RUN_LOG([$PERL --version])
 $PERL -e 'require 5.006;' || {