Tests: Fix testCTestResourceSpec struct initialization for some compilers

Some compilers do not like the nested `{{{}}}` member initialization
syntax, so use just `{}`.  GCC 4.8 warns about the latter, so add a
suppression.

Fixes: #20097

CTestCustom.cmake.in

@@ -49,6 +49,7 @@ list(APPEND CTEST_CUSTOM_WARNING_EXCEPTION
   "WarningMessagesDialog\\.cxx"
   "warning.*directory name.*CMake-Xcode.*/bin/.*does not exist.*"
   "stl_deque.h:1051"
+  "Tests/CMakeLib/testCTestResourceSpec.cxx:.*warning: missing initializer for member.*cmCTestResourceSpec::.*" # GCC 4.8 disagrees with later compilers on C++11 initializer list conversion
   "(Lexer|Parser).*warning.*conversion.*may (alter its value|change the sign)"
   "(Lexer|Parser).*warning.*(statement is unreachable|will never be executed)"
   "(Lexer|Parser).*warning.*variable.*was set but never used"

Tests/CMakeLib/testCTestResourceSpec.cxx

@@ -21,43 +21,42 @@ static const std::vector<ExpectedSpec> expectedResourceSpecs = {
     {"threads", {
     }},
   }}}},
-  {"spec2.json", true, {{{
-  }}}},
-  {"spec3.json", false, {{{}}}},
-  {"spec4.json", false, {{{}}}},
-  {"spec5.json", false, {{{}}}},
-  {"spec6.json", false, {{{}}}},
-  {"spec7.json", false, {{{}}}},
-  {"spec8.json", false, {{{}}}},
-  {"spec9.json", false, {{{}}}},
-  {"spec10.json", false, {{{}}}},
-  {"spec11.json", false, {{{}}}},
-  {"spec12.json", false, {{{}}}},
-  {"spec13.json", false, {{{}}}},
-  {"spec14.json", true, {{{}}}},
-  {"spec15.json", true, {{{}}}},
-  {"spec16.json", true, {{{}}}},
-  {"spec17.json", false, {{{}}}},
-  {"spec18.json", false, {{{}}}},
-  {"spec19.json", false, {{{}}}},
-  {"spec20.json", true, {{{}}}},
-  {"spec21.json", false, {{{}}}},
-  {"spec22.json", false, {{{}}}},
-  {"spec23.json", false, {{{}}}},
-  {"spec24.json", false, {{{}}}},
-  {"spec25.json", false, {{{}}}},
-  {"spec26.json", false, {{{}}}},
-  {"spec27.json", false, {{{}}}},
-  {"spec28.json", false, {{{}}}},
-  {"spec29.json", false, {{{}}}},
-  {"spec30.json", false, {{{}}}},
-  {"spec31.json", false, {{{}}}},
-  {"spec32.json", false, {{{}}}},
-  {"spec33.json", false, {{{}}}},
-  {"spec34.json", false, {{{}}}},
-  {"spec35.json", false, {{{}}}},
-  {"spec36.json", false, {{{}}}},
-  {"noexist.json", false, {{{}}}},
+  {"spec2.json", true, {}},
+  {"spec3.json", false, {}},
+  {"spec4.json", false, {}},
+  {"spec5.json", false, {}},
+  {"spec6.json", false, {}},
+  {"spec7.json", false, {}},
+  {"spec8.json", false, {}},
+  {"spec9.json", false, {}},
+  {"spec10.json", false, {}},
+  {"spec11.json", false, {}},
+  {"spec12.json", false, {}},
+  {"spec13.json", false, {}},
+  {"spec14.json", true, {}},
+  {"spec15.json", true, {}},
+  {"spec16.json", true, {}},
+  {"spec17.json", false, {}},
+  {"spec18.json", false, {}},
+  {"spec19.json", false, {}},
+  {"spec20.json", true, {}},
+  {"spec21.json", false, {}},
+  {"spec22.json", false, {}},
+  {"spec23.json", false, {}},
+  {"spec24.json", false, {}},
+  {"spec25.json", false, {}},
+  {"spec26.json", false, {}},
+  {"spec27.json", false, {}},
+  {"spec28.json", false, {}},
+  {"spec29.json", false, {}},
+  {"spec30.json", false, {}},
+  {"spec31.json", false, {}},
+  {"spec32.json", false, {}},
+  {"spec33.json", false, {}},
+  {"spec34.json", false, {}},
+  {"spec35.json", false, {}},
+  {"spec36.json", false, {}},
+  {"noexist.json", false, {}},
   /* clang-format on */
 };