Merge pull request #20985 from benpicco/picolibc-endian.h

sys/endian: fix build with picolibc

sys/include/endian.h

@@ -94,31 +94,79 @@ uint64_t le64toh(uint64_t little_endian_64bits);/**< little endian to host, 64 b
 #endif
 
 #if BYTE_ORDER == LITTLE_ENDIAN
+#  ifndef htobe16
 #  define htobe16(_x) __builtin_bswap16(_x)
+#  endif
+#  ifndef htole16
 #  define htole16(_x) ((uint16_t)(_x))
+#  endif
+#  ifndef be16toh
 #  define be16toh(_x) __builtin_bswap16(_x)
+#  endif
+#  ifndef le16toh
 #  define le16toh(_x) ((uint16_t)(_x))
+#  endif
+#  ifndef htobe32
 #  define htobe32(_x) __builtin_bswap32(_x)
+#  endif
+#  ifndef htole32
 #  define htole32(_x) ((uint32_t)(_x))
+#  endif
+#  ifndef be32toh
 #  define be32toh(_x) __builtin_bswap32(_x)
+#  endif
+#  ifndef le32toh
 #  define le32toh(_x) ((uint32_t)(_x))
+#  endif
+#  ifndef htobe64
 #  define htobe64(_x) __builtin_bswap64(_x)
+#  endif
+#  ifndef htole64
 #  define htole64(_x) ((uint64_t)(_x))
+#  endif
+#  ifndef be64toh
 #  define be64toh(_x) __builtin_bswap64(_x)
+#  endif
+#  ifndef le64toh
 #  define le64toh(_x) ((uint64_t)(_x))
+#  endif
 #elif BYTE_ORDER == BIG_ENDIAN
+#  ifndef htole16
 #  define htole16(_x) __builtin_bswap16(_x)
+#  endif
+#  ifndef htobe16
 #  define htobe16(_x) ((uint16_t)(_x))
+#  endif
+#  ifndef le16toh
 #  define le16toh(_x) __builtin_bswap16(_x)
+#  endif
+#  ifndef be16toh
 #  define be16toh(_x) ((uint16_t)(_x))
+#  endif
+#  ifndef htole32
 #  define htole32(_x) __builtin_bswap32(_x)
+#  endif
+#  ifndef htobe32
 #  define htobe32(_x) ((uint32_t)(_x))
+#  endif
+#  ifndef le32toh
 #  define le32toh(_x) __builtin_bswap32(_x)
+#  endif
+#  ifndef be32toh
 #  define be32toh(_x) ((uint32_t)(_x))
+#  endif
+#  ifndef htole64
 #  define htole64(_x) __builtin_bswap64(_x)
+#  endif
+#  ifndef htobe64
 #  define htobe64(_x) ((uint64_t)(_x))
+#  endif
+#  ifndef le64toh
 #  define le64toh(_x) __builtin_bswap64(_x)
+#  endif
+#  ifndef be64toh
 #  define be64toh(_x) ((uint64_t)(_x))
+#  endif
 #else
 #  error "Byte order not supported"
 #endif