Index: /usr/src/sys/modules/zfs/Makefile
===================================================================
--- /usr/src/sys/modules/zfs/Makefile	(revision 311147)
+++ /usr/src/sys/modules/zfs/Makefile	(working copy)
@@ -94,8 +94,14 @@
 CFLAGS+=-DBUILDING_ZFS
 
 .if ${MACHINE_ARCH} == "powerpc64"
+.include <bsd.compiler.mk>
+.if ${COMPILER_TYPE} == "gcc"
+# gcc421 requires the -mminimal-toc .
+# But clang 3.9.1 disallows it and does not need it.
+# more modern gcc's allow it.
 CFLAGS+=-mminimal-toc
 .endif
+.endif
 
 .ifdef ZFS_DEBUG
 CFLAGS+=-DDEBUG=1