fixes for compiling with gcc 10

gcc 10 no longer lets you get away with not externing global variables in header files. This adds the necessary extern and adds defines in appropriate c files

nyx/nyx_gui/storage/nx_emmc.c

@@ -21,6 +21,10 @@
 #include "../mem/heap.h"
 #include "../utils/list.h"
 
+sdmmc_t emmc_sdmmc;
+sdmmc_storage_t emmc_storage;
+FATFS emmc_fs;
+
 void nx_emmc_gpt_parse(link_t *gpt, sdmmc_storage_t *storage)
 {
 	gpt_t *gpt_buf = (gpt_t *)calloc(NX_GPT_NUM_BLOCKS, NX_EMMC_BLOCKSIZE);