baremetal: create an assert_fail C helper

Create a test for it under interactive/assert_fail.c

Move prompt under interactive

Create baremetal/arch/aarch64/c_from_as.S as an example of calling C
functions from assembly.

build-baremetal

@@ -15,6 +15,7 @@ class BaremetalComponent(common.Component):
             '-mcpu={}'.format(common.mcpu), common.Newline,
             '-nostartfiles', common.Newline,
             '-O0', common.Newline,
+            '-I', common.baremetal_src_lib_dir, common.Newline,
         ]
         if args.prebuilt:
             gcc = 'arm-none-eabi-gcc'