configure support for extended test suite

Add a configure argument to enable extended test suite.
The extended test suite is disabled by default (and thus
will not be run in vanilla Swift CI jobs).

Move yet another intermittently failing test,
dispatch_suspend_timer, out of the list of default tests.

Signed-off-by: Daniel A. Steffen <dsteffen@apple.com>

Author: dgrove-oss

configure.ac

@@ -174,6 +174,18 @@ AC_SUBST([SWIFT_LIBDIR])
 AC_CHECK_PROG(use_gold_linker, ld.gold, true, false)
 AM_CONDITIONAL(USE_GOLD_LINKER, $use_gold_linker)
 
+#
+# Enable an extended test suite that includes
+# tests that are too unreliable to be enabled by
+# default in the Swift CI environment, but are still
+# useful for libdispatch developers to be able to run.
+#
+AC_ARG_ENABLE([extended-test-suite],
+  [AS_HELP_STRING([--enable-extended-test-suite],
+    [Include additional test cases that may fail intermittently])]
+)
+AM_CONDITIONAL(EXTENDED_TEST_SUITE, test "x$enable_extended_test_suite" = "xyes")
+
 #
 # Enable __thread based TSD on platforms where it is efficient
 # Allow override based on command line argument to configure