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/arch/x86-64.h

@@ -64,7 +64,19 @@
   syscall; \
   ret;
 
+#ifdef ENABLE_INIT_FINI
 /*
+ * call libc_init_array
+ */
+#define _INIT             \
+  call libc_init_array;
+#else /* !ENABLE_INIT_FINI */
+#define _INIT
+#endif /* ENABLE_INIT_FINI */
+
+/*
+ * call libc_init_array
+ *
  * mov argc ([%rsp]) -> %rdi
  * mov argv (%rsp + 0x8) -> %rsi
  *
@@ -76,15 +88,17 @@
  * infinite loop
  */
 #define _START            \
-   mov (%rsp), %rdi;      \
-   mov %rsp, %rsi;        \
-   add $8, %rsi;          \
-   callq main;            \
+  _INIT;                  \
                           \
-   mov %rax, %rdi;        \
-   callq exit;            \
-   1:                     \
-   jmp 1b
+  mov (%rsp), %rdi;       \
+  mov %rsp, %rsi;         \
+  add $8, %rsi;           \
+  callq main;             \
+                          \
+  mov %rax, %rdi;         \
+  callq exit;             \
+  1:                      \
+  jmp 1b;
 
 /*
  * setjmp