build: prevent binary downloads for non x86 architectures

download_externals: Add check for i686 and i386 (in addition
to the current x86_64) and exit if not one of the three.

ASTERISK-26497

Change-Id: Ia4d429fcefa5b2f5b6e99159d4607de8e8325b2f

build_tools/download_externals

@@ -73,8 +73,13 @@ major_version=${major_version}.0
 
 if [[ "${HOST_CPU}" = "x86_64" ]] ; then
 	host_bits=64
-else
+elif [[ "${HOST_CPU}" = "i386" ]] ; then
+	host_bits=32
+elif [[ "${HOST_CPU}" = "i686" ]] ; then
 	host_bits=32
+else
+	echo "${module_name}: External module downloading is not available for the ${HOST_CPU} platform.  Only x86 based platforms are currently supported.  Please disable this module in menuselect."
+	exit 1
 fi
 
 if [[ -z "${variant}" ]] ; then