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/arm-v7.h

@@ -80,24 +80,37 @@
   \
   pop {r4-r12, pc};
 
+#ifdef ENABLE_INIT_FINI
 /*
+ * bl libc_init_array
+ */
+#define _INIT           \
+  bl libc_init_array;
+#else /* !ENABLE_INIT_FINI */
+#define _INIT
+#endif /* ENABLE_INIT_FINI */
+
+/*
+ * bl libc_init_array
+ *
  * ldr argc ([sp + 0x0]) -> r0
  * add argv (sp + 0x4) -> r1
- *
  * bl main
  *
  * bl exit
  *
  * infinite loop
  */
-#define _START            \
-   ldr r0, [sp, #0];      \
-   add r1, sp, #4;        \
-   bl main;               \
-                          \
-   bl exit;               \
-   1:                     \
-   b 1b
+#define _START          \
+  _INIT;                \
+                        \
+  ldr r0, [sp, #0];     \
+  add r1, sp, #4;       \
+  bl main;              \
+                        \
+  bl exit;              \
+  1:                    \
+  b 1b;
 
 /**
  * If hard-float mode: