Add support for init/fini arrays to libc (#1725)

The arrays contain the addresses of functions annotated with
constructor or destructor attributes. The support is optional,
requires FEATURE_INIT_FINI cmake option to be set. As of now, the
option is _not_ available in tools/build.py directly, only via
`--cmake-param="-DFEATURE_INIT_FINI=ON"`.

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-libc/target/posix/jerry-libc-target.c

@@ -51,6 +51,10 @@ long int syscall_3 (long int syscall_no, long int arg1, long int arg2, long int
 void __attr_noreturn___ __attr_used___
 exit (int status) /**< status code */
 {
+#ifdef ENABLE_INIT_FINI
+  libc_fini_array ();
+#endif /* ENABLE_INIT_FINI */
+
   syscall_1 (SYSCALL_NO (close), (long int) stdin);
   syscall_1 (SYSCALL_NO (close), (long int) stdout);
   syscall_1 (SYSCALL_NO (close), (long int) stderr);