print cmark test failures from CTest

Author: QuietMisdreavus

utils/swift_build_support/swift_build_support/products/cmark.py

@@ -70,6 +70,8 @@ def build(self, host_target):
             toolchain_file = self.generate_linux_toolchain_file(platform, arch)
             self.cmake_options.define('CMAKE_TOOLCHAIN_FILE:PATH', toolchain_file)
 
+        self.cmake_options.define('CTEST_OUTPUT_ON_FAILURE', 'ON')
+
         self.build_with_cmake(["all"], self.args.cmark_build_variant, [])
 
     def should_test(self, host_target):