tests: merged some testsuite fixlets

* fix-cxx-libtool-demo:
  tests: avoid failure due to libtool quirks in C++ demo test

* subdir-objects-pr10697:
  tests: fix spurious failures due to missing '$sleep'

* subdirs-simplify:
  subdir tests: avoid an use of "make -j4", for portability

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

diff --combined t/cxx-lt-demo.sh
index 3c931e0,0ccd953,3c931e0,3c931e0..c110435
--- 1/t/cxx-lt-demo.sh
--- 2/t/cxx-lt-demo.sh
--- 3/t/cxx-lt-demo.sh
--- 4/t/cxx-lt-demo.sh
+++ b/t/cxx-lt-demo.sh
@@@@@ -53,7 -53,7 -53,7 -53,7 +53,7 @@@@@ TESTS = try.s
    check-local: test-objs
    test-objs:
        test -f src/main.$(OBJEXT)
 -      test -f lib/libfoo.$(OBJEXT)
 +      test -f lib/libfoo.lo
    END
    
    cat > src/Makefile.am << 'END'
@@@@@ -128,6 -128,6 -128,6 -128,6 +128,6 @@@@@ $MAKE test-obj
    VERBOSE=yes $MAKE check-TESTS
    grep 'Howdy.*Testsuite' try.log || grep 'Skip:.*cross-compiled' try.log
    
- --$MAKE -e CC=false distcheck
+ ++$MAKE distcheck
    
    :