MDEV-24130: Cannot launch mariadbd via mysqld_safe

- Patch 95bb3cb8 used `my_which` function in `10.2`
- Based on patch `355ee687` from 10.3+ `command -v` is used instead of
`my_which` so we are changing in this patch also
- `ldconfig` is usually found in `/sbin` so make sure it is added in
`$PATH` variable

scripts/mysqld_safe.sh

@@ -440,7 +440,8 @@ mysqld_ld_preload_text() {
 set_malloc_lib() {
   malloc_lib="$1"
   if expr "$malloc_lib" : "\(tcmalloc\|jemalloc\)" > /dev/null ; then
-    if ! my_which ldconfig > /dev/null 2>&1
+    export PATH=$PATH:/sbin
+    if ! command -v ldconfig > /dev/null 2>&1
     then
       log_error "ldconfig command not found, required for ldconfig -p"
       exit 1