Enable MK_TESTS by default.

This was never intended to be off by default but was done this way
because the initial patches broke the build.  Things seem stable now
(have been so for a while too) and "make tinderbox" is clean so let's
try again.

Announced in freebsd-current; all reported shortcomings have been
addressed.

share/mk/src.opts.mk

@@ -143,6 +143,7 @@ __DEFAULT_YES_OPTIONS = \
     SYSINSTALL \
     TCSH \
     TELNET \
+    TESTS \
     TEXTPROC \
     UNBOUND \
     USB \
@@ -168,7 +169,6 @@ __DEFAULT_NO_OPTIONS = \
     SHARED_TOOLCHAIN \
     SORT_THREADS \
     SVN \
-    TESTS \
     USB_GADGET_EXAMPLES
 
 #

tools/build/options/WITHOUT_TESTS

@@ -0,0 +1,9 @@
+.\" $FreeBSD$
+Set to not build nor install the
+.Fx
+Test Suite in
+.Pa /usr/tests/ .
+See
+.Xr tests 7
+for more details.
+This also disables the build of all test-related dependencies, including ATF.

tools/build/options/WITH_TESTS

@@ -1,8 +0,0 @@
-.\" $FreeBSD$
-Set to install the
-.Fx
-Test Suite in
-.Pa /usr/tests/ .
-See
-.Xr tests 7
-for more details.