extra/boost: v8 update

extra/boost/PKGBUILD

@@ -10,6 +10,7 @@
 #  - changed _bindir to .linuxarm from .linuxx86
 #  - removed (optional) dep to openmpi - does not build on ARM
 #  - build armv6h with -march=armv6k
+#  - specify arm architecture to b2 for aarch64
 
 pkgbase=boost
 pkgname=('boost-libs' 'boost')
@@ -59,6 +60,7 @@ build() {
    # --layout=system no longer adds the -mt suffix for multi-threaded libs.
    # install to ${_stagedir} in preparation for split packaging
    "${_stagedir}"/bin/b2 \
+      architecture=arm \
       variant=release \
       debug-symbols=off \
       threading=multi \