Fix CI build errors

Author: dgarske

src/boot_riscv.c

@@ -273,7 +273,7 @@ void do_boot(const uint32_t *app_offset)
     unsigned long dts_addr;
     hal_dts_fixup((uint32_t*)dts_offset);
     dts_addr = (unsigned long)dts_offset;
-#else
+#elif defined(WOLFBOOT_RISCV_MMODE) || __riscv_xlen == 64
     unsigned long dts_addr = 0;
 #endif
 

src/string.c

@@ -30,7 +30,7 @@
 #if defined(_RENESAS_RA_)
 #include <stdint.h>
 #endif
-#ifndef TARGET_library
+#if !defined(TARGET_library) && defined(__STDC_HOSTED__) && __STDC_HOSTED__
 #include <string.h>
 #else
 size_t strlen(const char *s); /* forward declaration */