[fusl] Remove code for unsupported architectures

fusl/src/ldso/arm/find_exidx.c

-#define _GNU_SOURCE
-#include <link.h>
-#include <stdint.h>
-
-struct find_exidx_data {
-  uintptr_t pc, exidx_start;
-  int exidx_len;
-};
-
-static int find_exidx(struct dl_phdr_info* info, size_t size, void* ptr) {
-  struct find_exidx_data* data = ptr;
-  const ElfW(Phdr)* phdr = info->dlpi_phdr;
-  uintptr_t addr, exidx_start = 0;
-  int i, match = 0, exidx_len = 0;
-
-  for (i = info->dlpi_phnum; i > 0; i--, phdr++) {
-    addr = info->dlpi_addr + phdr->p_vaddr;
-    switch (phdr->p_type) {
-      case PT_LOAD:
-        match |= data->pc >= addr && data->pc < addr + phdr->p_memsz;
-        break;
-      case PT_ARM_EXIDX:
-        exidx_start = addr;
-        exidx_len = phdr->p_memsz;
-        break;
-    }
-  }
-  data->exidx_start = exidx_start;
-  data->exidx_len = exidx_len;
-  return match;
-}
-
-uintptr_t __gnu_Unwind_Find_exidx(uintptr_t pc, int* pcount) {
-  struct find_exidx_data data;
-  data.pc = pc;
-  if (dl_iterate_phdr(find_exidx, &data) <= 0)
-    return 0;
-  *pcount = data.exidx_len / 8;
-  return data.exidx_start;
-}