Fix endianess detection

tests/unit/endian.h

@@ -41,7 +41,8 @@
 # elif (__BYTE_ORDER == __PDP_ENDIAN)
 #  define BOOST_PDP_ENDIAN
 # else
-#  error Unknown machine endianness detected.
+// Failsafe
+#  define BOOST_LITTLE_ENDIAN
 # endif
 # define BOOST_BYTE_ORDER __BYTE_ORDER
 #elif defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)
@@ -50,11 +51,14 @@
 #elif defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)
 # define BOOST_LITTLE_ENDIAN
 # define BOOST_BYTE_ORDER 1234
+// https://developer.arm.com/documentation/dui0491/i/Compiler-specific-Features/Predefined-macros
 #elif defined(__sparc) || defined(__sparc__) \
    || defined(_POWER) || defined(__powerpc__) \
    || defined(__ppc__) || defined(__hpux) || defined(__hppa) \
    || defined(_MIPSEB) || defined(_POWER) \
-   || defined(__s390__)
+   || defined(__s390__) \
+   || defined(__ARMEB__) || defined(__AARCH64EB__) \
+   || defined(__BIG_ENDIAN) || defined(__ARM_BIG_ENDIAN)
 # define BOOST_BIG_ENDIAN
 # define BOOST_BYTE_ORDER 4321
 #elif defined(__i386__) || defined(__alpha__) \
@@ -63,12 +67,17 @@
    || defined(_M_ALPHA) || defined(__amd64) \
    || defined(__amd64__) || defined(_M_AMD64) \
    || defined(__x86_64) || defined(__x86_64__) \
-   || defined(_M_X64) || defined(__bfin__)
-
+   || defined(_M_X64) || defined(__bfin__) \
+   || defined(__ARMEL__) || defined(__AARCH64EL__) \
+   || defined(__arm64__) || defined(__arm__)
 # define BOOST_LITTLE_ENDIAN
 # define BOOST_BYTE_ORDER 1234
 #else
-# error The file boost/detail/endian.hpp needs to be set up for your CPU type.
+
+// Failsafe
+# define BOOST_LITTLE_ENDIAN
+# define BOOST_BYTE_ORDER 1234
+
 #endif