build.sh: facilitate fat binary builds on MacOS.

build.sh

@@ -1,4 +1,5 @@
-#!/bin/sh -e
+#!/bin/sh
+set -e
 #
 # The script allows to override 'CC', 'CFLAGS' and 'flavour' at command
 # line, as well as specify additional compiler flags. For example to
@@ -43,6 +44,13 @@ while [ "x$1" != "x" ]; do
         -shared)    shared=1;;
         -dll)       shared=1; dll=".dll";;
         -m*)        CFLAGS="$CFLAGS $1";;
+        -target|-arch)
+                    if expr "$CFLAGS" : ".*-arch " >/dev/null; then
+                        cflags="$cflags $1 $2"
+                    else
+                        CFLAGS="$CFLAGS $1 $2"
+                    fi
+                    shift;;
         -*target*)  CFLAGS="$CFLAGS $1";;
         -*)         cflags="$cflags $1";;
         *=*)        eval "$1";;
@@ -76,9 +84,11 @@ if [ -z "${CROSS_COMPILE}${AR}" ] && echo ${predefs} | grep -q clang; then
        env PATH="$search_dirs:$PATH" which llvm-ar > /dev/null 2>&1; then
         PATH="$search_dirs:$PATH"
         AR=llvm-ar
+        RANLIB=llvm-ranlib
     fi
 fi
 AR=${AR:-${CROSS_COMPILE}ar}
+RANLIB=${RANLIB:-${CROSS_COMPILE}ranlib}
 
 if echo ${predefs} | grep -q x86_64; then
     if (grep -q -e '^flags.*\badx\b' /proc/cpuinfo) 2>/dev/null; then
@@ -101,6 +111,7 @@ trap '[ $? -ne 0 ] && rm -f libblst.a; rm -f *.o ${TMPDIR}/*.blst.$$' 0
 (set -x; ${CC} ${CFLAGS} -c ${TOP}/src/server.c)
 (set -x; ${CC} ${CFLAGS} -c ${TOP}/build/assembly.S)
 (set -x; ${AR} rc libblst.a *.o)
+which ${RANLIB} > /dev/null 2>&1 && (set -x; ${RANLIB} libblst.a)
 
 if [ $shared ]; then
     case $flavour in