MDEV-21646: postfix - my_addr_resolve: static Dl_info info

Encountered the linker failure on Debug build in 10.4:

[53/585] Linking CXX executable unittest/sql/mf_iocache-t
FAILED: unittest/sql/mf_iocache-t
: && /usr/bin/c++  -pie -fPIC -fstack-protector --param=ssp-buffer-size=4 -fPIC -g -DENABLED_DEBUG_SYNC -ggdb3 -DSAFE_MUTEX -DSAFEMALLOC -DTRASH_FREED_MEMORY -Wall -Wextra -Wno-format-truncation -Wno-init-self -Wno-nonnull-compare -Wno-unused-parameter -Woverloaded-virtual -Wnon-virtual-dtor -Wvla -Wwrite-strings -Werror  -Wl,-z,relro,-z,now unittest/sql/CMakeFiles/mf_iocache-t.dir/mf_iocache-t.cc.o unittest/sql/CMakeFiles/mf_iocache-t.dir/__/__/sql/mf_iocache_encr.cc.o  -o unittest/sql/mf_iocache-t  -lpthread  mysys/libmysys.a  unittest/mytap/libmytap.a  mysys_ssl/libmysys_ssl.a  mysys/libmysys.a  dbug/libdbug.a  mysys/libmysys.a  dbug/libdbug.a  -lz  -lm  strings/libstrings.a  -lpthread  -lssl  -lcrypto  -ldl && :
/usr/bin/ld: mysys/libmysys.a(my_addr_resolve.c.o):/home/dan/repos/mariadb-server-10.4/mysys/my_addr_resolve.c:173: multiple definition of `info'; unittest/sql/CMakeFiles/mf_iocache-t.dir/mf_iocache-t.cc.o:/home/dan/repos/mariadb-server-10.4/unittest/sql/mf_iocache-t.cc:99: first defined here

We make Dl_info static as in MDEV-21646 moving it out of the function
was the main goal and having it scope limited by static doesn't affect
the function.

mysys/my_addr_resolve.c

@@ -170,7 +170,7 @@ static pid_t pid;
 static char addr2line_binary[1024];
 static char output[1024];
 static struct pollfd poll_fds;
-Dl_info info;
+static Dl_info info;
 
 int start_addr2line_fork(const char *binary_path)
 {