systemc: set endianess to fix build for ARM host

ARM architectures were not covered in the endianess #if cases, which
lead the build to fail on an arm host with message:

error The file boost/detail/endian.hpp needs to be set up for your CPU
type.

Change-Id: Id012cf37810da113174a51746e290e25138739cb
Reviewed-on: https://gem5-review.googlesource.com/c/14595
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
diff --git a/src/systemc/ext/utils/endian.hh b/src/systemc/ext/utils/endian.hh
index fcf47e8..86e05cc 100644
--- a/src/systemc/ext/utils/endian.hh
+++ b/src/systemc/ext/utils/endian.hh
@@ -67,7 +67,8 @@
    || 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(__arm__) || defined(__aarch64__)
 
 # define SC_BOOST_LITTLE_ENDIAN
 # define SC_BOOST_BYTE_ORDER 1234