Testing based on MACHINE_ARCH is problematic. Default to yes to build

clang.  A separate change will fix buildworld to default to yes or no
based on the target.

share/mk/bsd.own.mk

@@ -281,18 +281,6 @@ WITH_HESIOD=
 WITH_IDEA=
 .endif
 
-#
-# Default behaviour of MK_CLANG depends on the architecture.
-#
-.if ${MACHINE_ARCH} == "amd64" || ${MACHINE_ARCH} == "i386" || \
-    ${MACHINE_ARCH} == "powerpc"
-_clang_yes=CLANG
-_clang_no=
-.else
-_clang_yes=
-_clang_no=CLANG
-.endif
-
 #
 # MK_* options which default to "yes".
 #
@@ -320,7 +308,7 @@ _clang_no=CLANG
     BZIP2 \
     CALENDAR \
     CDDL \
-    ${_clang_yes} \
+    CLANG \
     CPP \
     CRYPT \
     CTM \
@@ -424,7 +412,6 @@ MK_${var}:=	yes
     BIND_SIGCHASE \
     BIND_XML \
     BSD_GREP \
-    ${_clang_no} \
     GPIO \
     HESIOD \
     IDEA