configure: Use linker hardening flags on mingw

This makes it consistent with the msvc builds which automatically set
the DEP and ASLR flags by default.  There really is no good reason why
they shouldn't be set.

The fact that binutils does not set them on by default boggles the mind.
Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -3029,6 +3029,8 @@ case $target_os in
         elif enabled arm; then
             LIBTARGET=arm-wince
         fi
+        check_ldflags -Wl,--nxcompat
+        check_ldflags -Wl,--dynamicbase
         shlibdir_default="$bindir_default"
         SLIBPREF=""
         SLIBSUF=".dll"