AP_Common: provide minimal byteswap.h and endian.h

libraries/AP_Common/missing/byteswap.h

@@ -0,0 +1,24 @@
+#if defined(HAVE_BYTESWAP_H) && HAVE_BYTESWAP_H
+#include_next <byteswap.h>
+#else
+
+#include <inttypes.h>
+
+/* minimal version defining only the macros we need in our codebase */
+
+static inline uint16_t __bswap_16(uint16_t u)
+{
+    return (uint16_t) __builtin_bswap16(u);
+}
+
+static inline uint32_t __bswap_32(uint32_t u)
+{
+    return (uint32_t) __builtin_bswap32(u);
+}
+
+static inline uint64_t __bswap_64(uint64_t u)
+{
+    return (uint64_t) __builtin_bswap64(u);
+}
+
+#endif

libraries/AP_Common/missing/endian.h

@@ -0,0 +1,16 @@
+#if defined(HAVE_ENDIAN_H) && HAVE_ENDIAN_H
+#include_next <endian.h>
+#else
+
+/* minimal version defining only the macros we need in our codebase */
+
+#define __LITTLE_ENDIAN  1234
+#define __BIG_ENDIAN     4321
+
+#ifdef __ARMEB__
+#define __BYTE_ORDER     __BIG_ENDIAN
+#else
+#define __BYTE_ORDER     __LITTLE_ENDIAN
+#endif
+
+#endif