Cherry-picked from upstream SVN rev 232322

--- a/src/share/mk/bsd.own.mk
+++ b/src/share/mk/bsd.own.mk
@@ -413,6 +413,7 @@
     BIND_LIBS \
     BIND_SIGCHASE \
     BIND_XML \
+    CLANG_IS_CC \
     HESIOD \
     ICONV \
     IDEA \
@@ -561,6 +562,10 @@
 MK_GDB:=	no
 .endif
 
+.if ${MK_CLANG} == "no"
+MK_CLANG_IS_CC:= no
+.endif
+
 #
 # Set defaults for the MK_*_SUPPORT variables.
 #