run: Use GLIBC_TUNABLES instead of MALLOC_PERTURB_

glibc 2.34 removed MALLOC_CHECK_ and MALLOC_PERTURB_ and replaced them
with GLIBC_TUNABLES with a completely different syntax and requiring a
special library (libc_malloc_debug.so.0) to be preloaded.

Note this works even if the preloaded library is not present since
ld.so ignores missing LD_PRELOAD.  So this shouldn't break anything
either for older glibc or if the special library is missing.

(cherry picked from virt-v2v commit 9f54a4063ddcda91a7bb965c343178da419a8726)

Author: rwmjones

run.in

@@ -103,7 +103,9 @@ fi
 # This is a cheap way to find some use-after-free and uninitialized
 # read problems when using glibc.
 random_val="$(@AWK@ 'BEGIN{srand(); print 1+int(255*rand())}' < /dev/null)"
-export MALLOC_PERTURB_=$random_val
+LD_PRELOAD="${LD_PRELOAD:+"$LD_PRELOAD:"}libc_malloc_debug.so.0"
+GLIBC_TUNABLES=glibc.malloc.check=1:glibc.malloc.perturb=$random_val
+export LD_PRELOAD GLIBC_TUNABLES
 
 # Do we have libtool?  If we have it then we can use it to make
 # running valgrind simpler.  However don't depend on it.