test/mkmf/test_flags.rb: try to suppress random CI failure

on AIX ppc
https://rubyci.org/logs/rubyci.s3.amazonaws.com/aix71_ppc/ruby-trunk/log/20181226T113305Z.fail.html.gz

test/lib/test/unit/assertions.rb: ditto, for TestIO#test_copy_stream_no_busy_wait

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66591 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/lib/test/unit/assertions.rb

@@ -761,7 +761,7 @@ eom
         # [ruby-core:81540]
         min_hz = windows? ? 67 : 100
         min_measurable = 1.0 / min_hz
-        min_measurable *= 1.10 # add a little (10%) to account for misc. overheads
+        min_measurable *= 1.30 # add a little (30%) to account for misc. overheads
         if max < min_measurable
           max = min_measurable
         end

test/mkmf/test_flags.rb

@@ -41,7 +41,7 @@ class TestMkmf
     end
 
     def test_try_cflag_invalid_opt
-      assert_separately([], <<-'end;') #do
+      assert_separately([], <<-'end;', timeout: 30) #do
         assert(!try_cflags("nosuch.c"), TestMkmf::MKMFLOG)
         assert(have_devel?, TestMkmf::MKMFLOG)
       end;