Core target arch support for conditional compilation of SUBDIRs

which is used by libspl for it's arch specific atomic implementations.

autogen.sh

@@ -3,6 +3,6 @@
 aclocal -I config &&
 libtoolize --automake --copy
 autoheader &&
-automake --add-missing --include-deps --copy 2>/dev/null
+automake --add-missing --include-deps --copy
 autoconf
 rm -rf autom4te.cache aclocal.m4

config/user-arch.m4

@@ -0,0 +1,21 @@
+dnl #
+dnl # Set the target arch for libspl atomic implementation
+dnl #
+AC_DEFUN([ZFS_AC_CONFIG_USER_ARCH], [
+	AC_MSG_CHECKING(for target arch)
+	TARGET_ARCH=`echo ${target_cpu} | sed -e s/i.86/i386/`
+	TARGET_ARCH_DIR=asm-$TARGET_ARCH
+        AC_MSG_RESULT([$TARGET_ARCH])
+
+	case $TARGET_ARCH in
+	i386|x86_64|powerpc)
+		AC_SUBST([TARGET_ARCH])
+		AC_SUBST([TARGET_ARCH_DIR])
+		;;
+	*)
+                AC_MSG_ERROR([
+		*** Unsupported architecture $TARGET_ARCH
+		*** Available architectures: x86, x86_64, powerpc])
+		;;
+	esac
+])

config/user.m4

@@ -2,6 +2,7 @@ dnl #
 dnl # Default ZFS user configuration
 dnl #
 AC_DEFUN([ZFS_AC_CONFIG_USER], [
+	ZFS_AC_CONFIG_USER_ARCH
 	ZFS_AC_CONFIG_USER_LIBEFI
 	ZFS_AC_CONFIG_USER_LIBDISKMGT
 	ZFS_AC_CONFIG_USER_LIBSHARE