src/task.c: Use b instead of br instruction on armv7l

Author: staticfloat

src/task.c

@@ -762,7 +762,7 @@ static void jl_start_fiber(jl_ucontext_t *lastt, jl_ucontext_t *t)
     asm(" mov sp, %0;\n"
         " mov lr, #0;\n" // Clear link register (lr) and frame pointer
         " mov fp, #0;\n" // (fp) to terminate unwinder.
-        " br %1;\n" // call `fn` with fake stack frame
+        " b %1;\n" // call `fn` with fake stack frame
         " udf #0" // abort
         : : "r" (stk), "r"(fn) : "memory" );
 #else