examples/hello_nim: Fix nimcache location

The Nim Example App fails to build because the `.nimcache` is located 2 folders up. This PR fixes the location of `.nimcache` in the `Makefile` of the Nim Example App.

`.nimcache` is explained in this article: https://lupyuen.github.io/articles/nim#inside-nim-on-nuttx

Author: lupyuen

examples/hello_nim/Makefile

@@ -30,8 +30,8 @@ MODULE    = $(CONFIG_EXAMPLES_HELLO_NIM)
 # Hello, World! Example
 
 NIMPATH = $(shell choosenim show path)
-CFLAGS += -I $(NIMPATH)/lib -I ./.nimcache
-CSRCS += $(wildcard .nimcache/*.c)
+CFLAGS += -I $(NIMPATH)/lib -I ../../.nimcache
+CSRCS += $(wildcard ../../.nimcache/*.c)
 
 MAINSRC = hello_nim_main.c